Samw here with this. Got one when DD was 4 mths as she was desperate to sit up, and it was great for me to be able to stick her in it and have her somewhere like the kitchen where it isn't really suitable for her to just lay on the floor, whilst I did washing, cooked etc.
I used it for feeding until recently, and still in fact use it for breakfast as we don't sit up at the table for that.
She's been able to get out of it since about 8 mths, but thats not really an issue for me, if I want her to be secure and out of the way now I'll stick her in the high chair.
Lastability? Well, I've caught DS1 (6) and DS2(4) sitting in it to watch the TV/ play games so I think she'll be using it as a chair for a good while yet! My only regret is that they didn't exist when DS1 was a baby!