Hi, we were away for 8 days and our in laws came to feed our cat twice a day.
Though I think it depends on the nature of the cat. Our cat is more than happy on his own, he likes his own space (infact he is quite unsociable!) and is on his own during daytime working hours. (He has a cat flap so he can let himself in and out but we always lock it at night so he cant go out incase a fox gets him or something).
When we were away, although I knew the in laws would take care of him I still worried about him missing us, but when we got back it was as if he didn't even realise we had been away.
The in laws did say however, that he was often asleep on our bed on my dressing gown so he could probably smell my scent on the dressing gown. Maybe it's a good idea to leave something of yours out so your cat can curl up on it!
On the other hand, our neighbours were away for nearly 2 weeks and we went round daily to feed their cat who is very affectionate. When our neighbours returned they said their cat wouldn't let them out her sight, so generally I think it does depend on the nature of your cat.