I've spent my first five Points into different Perks in the Skill Trees. But at Level 6, I decided to save my Points for later (when my Smithing-Skill is grown up). Now, with Level 8, I wanted to hand them out ... But... They're (3 points) all gone!
Do you know, if they expire after some time or levels?
Can I get them back?
They don't expire, I've done the same thing: hold onto skill points for several levels (currently, I have 5 unspent points).
If you haven't spent them, it sounds like you might've hit a bug. While there's a chance it might mark you a cheater (disputed), you can use the following console command to get back your skill points:
player.addperk <perk ID>
Where <perk ID> is replaced with the code for the perk you wanted to spend your points on. The UESP Wiki contains a list of these codes.
But before doing that, I'd double check your perk trees and make sure you didn't accidentally spend them.
