Yes they last longer IF you don't use powerflex ones (I must apologise as I keep mentioning it but if it was MY money i'd want to get the right ones.......)
There is something wrong with either powerflex's method or grade of poly. I used their upper arm bushes and they lasted 6 months and were completely shot. Fitted superflex to my bro's 147 and as far as I know they're still going well. I also used SF in lower arms on my 145 QV, which were still rock solid two years after fitting them. Prior to that I'd tried PF - about 8 months and knackered in a big way. Also PF don't use stainless bushings..which then rust and abrade on the bush.
I'll give PF their due for the rear hub bushes though - they're lasting well so far!
The poly bushes act like a bearing whereas most rubber ones locate firmly and utilise the "shore" of the rubber to allow twist. The difference on alfas is the upper arm bushes are ALREADY designed as a bearing, with a shaped sleeve / washer. They run dry though and then start to creak and wear. The lower arms are more conventional but the bushes will eventually separate from the shell. The 147/156/GT seem less prone than the 145 but then there's an additional bush in the lower arm where the fork of the strut attaches which probably firms things up a bit. You can tell if the lower arm bushes are shot as the car will "shift line" mid corner...
hth for starters?