Tri Shoes

Tri shoes? Or do you mean running shoes?

I change out my running shoes about every 3-4 months. That's the longest I can go without starting to feel shin splints start to creep up on me again.

A new pair will feel incredible.

tri shoes as in shoes for my bike... (cycling shoes)

Ahhh, that

If you're going to be doing flying squirrel mounts and dismounts, tri shoes make sense because they keep the shoe straps out of the cogs.

Other things about tri specific cycling shoes:
They have fewer attaching straps. Mine only have one strap to secure. They feel just as secure as my regular cycling shoes though.
They have drain holes in the bottom so when the pool water is still pouring out of your suit and down your legs it has a place to go rather than pool up inside your shoe.
They're a lot more open to the breeze, this dries my feet much better than regular cycling shoes so I have something close to dry feet when it's time to run.

Remember, though, that people use regular cycling shoes all the time and the longer the race the less a difference it makes which you go with.