It's not that big a deal to ride different crank lengths-- I've done it for years. You adjust almost instantly.
I ride 172.5 on the road. It's what came with the bike.
I ride 165 on the track-- I don't like long cranks on a steep track. I've tagged 165s on a 43 degree track without going down. I've seen people used to a shallow track show up on a steep one, bang their 170s on the banking, and go down.
I have 175 on the mountain bike - it's what came with the bike.
I ride the road bike at least 5 days a week, usually 6 or 7. I train and/or race at the track 2 days a week. A lot of times I'll do 60 miles in the morning on the road bike and then ~30 in the afternoon on the track bike. It's not a big deal to ride different length cranks.
I haven't been on the mountain bike for a while (too much road and track), but there have been times when I rode all three bikes in one day. It's not a big deal.
People worry way more about tiny things like crank length than they should. Just ride it and see how it feels.