Help... Building up to a longer run...

The 10% rule is a decent one for a general guideline, although even better would be to use a 12-18 week structured buildup along a progressive schedule by an expert, such as from one of the books by Higdon, Pfitzinger, or Galloway.

If you want to build to 8-10 miles max at a time, I suspect that if you're able to handle 4milers that often per week now, it won't be dangerous at all to throw one of those in per week. I'd be much more inclined to stick to a structured schedule if you really are starting to push your boundaries - I found them very useful when pushing to 40, 55, 70, than 85 miles per week progressively. 

Simple.  Add a mile a week until you reach your goal.  Just run slow, walk if necessary to keep your heart rate in zone 2 (i.e. easy conversational pace).  If that seems like too much, add 1/2 mile a week. 

That said, I think you'd be better off running for time over distance and extend the time by a few minutes each week for your long run as distance is not as good a measure of training volume, which is what you want to increase to get faster.  Lots of threads and book/articles on this concept.  Have fun.

I can run for a good hour now, but my HR is high.  After reading on these threads I am running slower and keeping my HR in the Z2/3 area.  Today I increased to 40 minutes and I am bored off my .  I want to go and my body says Go Joe run your off.  BUt I have to admit after almost a month now, going slower and buidling a little each week, 10% more or less, I do feel stronger.

The knees and other joints feel better.  I look forward to running and tell myself just stick to the slow build up.  early in July I went to far to fast and screwed my knee and ruined a race in August.  So my point is it's winter take your time and stick to the 10% rule.  IMHO

Joe

 Oh, Thanksgiving morning, I am running as far and fast as I can...gotta test that base building period......Yup all ready pciking out the tunes for the Ipod.

A rule that I've heard -- I'm not sure what the grounds for it are (if any) -- is that if you want to push your long run aggressively, you can add up to 20% to the long run, but keep total weekly volume increases to 10%.

My opinion -- and I'll probably get yelled at for saying this -- is that at low volume (<  20 miles/week), even this more aggressive rule is a bit too conservative for most people, unless that low volume really is already pushing your. A reasonably fit person (not terribly overweight, not a complete couch potato) can, I think, increase volume more quickly early on, but then level off later. For example, unless that 4miles 3x week is already tough for you (i.e., you are only just recovering, or maybe not even completely recovering, before the next run), you can be a bit more aggressive. Just monitor your body carefully and back off at the first sign of injury (for example, a pain that breaks your form, or a pain that doesn't go away by the next morning). And take an easy week (=lower volume) every so often (maybe every 4th week), and perhaps do a long run only once every other week for a while (but keep total volume up on 'off' (no long run) weeks, except when it is also an easy week).

So if it were me, I might try something like this for the next 4 weeks (assuming frequency stays at 3x/week, though it would be better to increase this to 4x/week): 4/4/6, 4/4/8. 5/4/9, 4/4/4. If, after week 4, you feel ready to do it again (i.e., increase some more), then you are good to go (but then perhaps add a 4th run per week, and get your increases closer to the 10% rule). If you didn't fully recover during week 4, back off. Anyway, something like that is what I personally would try, in your shoes.

Others will no doubt disagree. That's part of the fun of running -- ultimately, you have to figure it out for yourself.

While this doesn't exactly answer your question, if you're looking to improve your run during the colder weather, I'd recommend adding a fourth run per week (and even a fifth one) for now rather than extending one run.  Start with one mile on the fourth day and build up by a mile or so per week until you're at 4x4 miles.  Then start extending the long run one of the four milers by a mile a week.   Frequency helps a lot in building run fitness!

Brian 

 And how did you come to this conclusion, out of curiosity?

Personal experience as well as reading a few triathlon books (Friel, Sally Edwards, Brad Kearns).  In reality, though, it is just a mind trick since time and distance are all relative in the end.  However, personally, on long days I was getting hung up on running (or swimming or biking) a particular distance.  I found that if I focused on time I would tend to go further.  While time and distance are both ways to measure volume, as we (hopefully) get faster the 2 hour run which used to be a 12 miler, now becomes a 14 miler.  On the other hand, if I just say "I will run 12 miles" total training volume actually decreases as you get faster.  Of course, as you get faster you can just increase the distance of your run to achieve the same time.  As I said, it really is a mind trick in the end. 

So, time works better for you.  Because I've always trained by distance, and it seems to be doing the trick for me.  One is neither better nor worse than the other.

Neither is better or worse.  IMO, when you are starting out it is easier to extend a run for 2 minutes, than 2/10ths of a mile, which would be the same thing assuming a 10' pace. That is why I think (and some "experts" recommend) running by time is better than distance, at least at the beginning.