MY fatehr in law had a time capsule and router unit and it was great while it lasted… but it didn't last.
Apparently its a big issue with them and a lot of them have been failing at about 18 months (i.e. just outside the warranty). Apple don't want to know and there is a guy online who is collating a time capsule graveyard list (with the serial, date it died/length of use) which is rather telling as there are a LOT of them on his list and most are in the 18months of use range.
General opinion seems to be its a cooling issue as there is a hell of a lot of stuff in one small box with not enough air flow.
He's using a basic router and a seperate back up RAID 3 array instead now and thats working just fine.
Anyway thats what I've heard, hope it helps,
Badger