I have always put them on and then just never ever replaced them ha ha. I don't think they work very well. But if you're a fussy bastard you could put one on, but don't get a cheap one. It is sort of just as back up as most tanks have a filter in them.
won't do anything for your fuel pressure BUT the ones i picked up from auto-pro are see through so it eliminates having to take off the fuel lead from the carby to see if fuel is going through (not thats its a hard job...) just make sure you put it on the right way, as the ones i use have a one way valve on them Also can help when playing with the carby as you can tell when the bowl is full by watching the fuel flow through the filter and you can see once it's stopped.