Sprint performance has declined lately

The last two years, ever since I did a few long distance races, my sprint performances seem to have declined.  I feel fine, it's just my standing among other races, instead of improving has gone backwards.  

The only thing I can attribute it to, and I'm pretty sure I do this, is that I got in the habit of not pushing as hard as I could on the bike to save myself for the run.  I did this obviously for the distances events, and I'm thinking that mentality has been carrying itself over for sprints.  My average bike speed has gone down from when i started. I remember my first ever sprint race i averaged over 19 mph.  I haven't touched that speed since.  I can't believe I've gotten worse in 5 years.  I also remember my legs feeling like complete jello during my first two tri runs(both sprints) and i haven't had that feeling since.  I didn't know if that's a result of being used to it, or having not pushed as hard on the bike.

My question is, do you pretty much go all out on the bike during a sprint, or do you keep a little in the tank for the run?  All i have time for these days(have a new baby) is sprints so I'd like to improve as little as I can and trying to figure out whats happened.