I used to replace struts and mounts (don't forget the mounts!) at around 80k miles, but our old Caravan went over 150k w/o replacements and my '01 Neon is on par for about the same. Honestly, the car still drives and handles great.
I'll probably sell the car before I change the struts.
The Miata, otoh, does need them replaced. It's at 82k right now and I can feel that they're not what they should be.
I'm probably gonna go with basic KYB GR2 replacements.
As was already said, alignment is relative. You SHOULD have it aligned after replacing the struts or any other major susp. component, but in general if the tire wear is good, tire pressure is proper and overall track of the vehicle is straight, no alignment is necessary imho.