Long enough to get out of the way of the ones sprinting at 35 mph.

Actually, I try to avoid sprinting in triathlons if I can, - maybe to get by a clump of riders but mostly it's about going at a speed that you can maintain while remembering that you've got some mileage on foot to do after you get off the bike.

There's a lot more going on in something like a criterium. They're alternating between pushing hard and catching their breath while on somebody else's wheel.

They're both fun to watch for different reasons. Triathlons are better to watch if you can see them in the transitions. The pros are pretty amazing. Criteriums let you see the riders go by multiple times, but it's sort of like Nascar, it's not terribly interesting until the last few laps. At least not for me. It's pretty awesome though towards the end when the stronger teams make their move.