It's not the size of the album that counts, it's what you do with it!!
Three examples.
1) Dark Funeral's 'Diabolus Interium'- running time 36 minutes. Speedy, complex black metal which has plenty in it. Once it's over it feels complete. Plus I love pressing play again for a second round. Any longer and it'd probably get boring....
2) Anathema's 'Alternative 4'- running time 45 minutes. Gentle, brooding melancholy. Any longer and it would be stretching the feeling of the album. Any shorter and I'd feel short changed. The amount of emotion is just enough.
3) My Dying Bride's 'The Light at the End of the World'- running time 71 minutes. Epic, huge, atmospheric. The bigger the better. It could go over onto a second disk as far as I'm concerned!!
So, yes, I think albums can stretch from 36 to 71 minutes without feeling like I've wasted my money. They have to be good albums though!