BTW, the 20Vs metal petrol filter (pressurized) replacement intervals are very tricky. most of the time when u start to experience funny fuel related problems (e.g. fuel starvation, low fuel pressure [need EFN AFPR+meter shameless promo], or engine jerk), it will usually be the last thing ur mechanic checks. if its the first, good for u. some mechanics try the cheapest solution first (a lot of trial n error in our workshops actually).
bcoz the problem is easily associated with the ignition systems, plugs, fuel rail, fuel pump, injectors etc.. most ppl will miss it.
properly answering the question, there are no standard interval given by all manufacturers on when u should replace the filter. one brand might say 100k, another 80k. the silently accepted practice is once a year. why? bcoz this issue is VERY relative. the filter operates on the assumption that we have dirt in our fuel. sometimes some places, ppl have clean fuel tanks. so the filter may last longer (altho it is very hard to tell). some other ppl may have dirty fuel tank or it could be the petrol from under the petrol station itself is full of little dirt.
http://autorepair.about.com/cs/doityourself/a/aa082203a_2.htm
**please read the whole article
i'd go with replacing once every year or every 2 years (cheapskate!). it is totally up to u. if u can gauge how 'dirty' ur fuel might be, formulate ur own schedule. but changing petrol filter every 6 months even with driving in KL, not economic la. the filter can take more than that. besides the dust which may come from transport n storage, the only time ur fuel tank is exposed to dust would be when u open the cap to refuel.
im using proton Wira petrol filter for my 20V. dirt cheaper. as long as the fuel supply 17" nut is the same, any EFI petrol filter (metal) will do.