Why is there a rule that says babies must use a cot? We have a lovely cot and neither of my babies have ever used it to sleep in.
Yasin used it for a little while but was much happier moving from the hammock to a mattress on the floor. I tried Imran in the cot and he prefered the mattress on the floor too.
Imran is a little over a year and he still loves his hammock for day sleeps.

I wouldn't say the cot was a total waste of money - it's a safe space for the cat and folded washing and Yasin likes me to put him in there so he can bounce on the inner-spring mattress.