How do I know if my MAF's on its way out?

I've done some searching about for this but not found anything that definitively answers my particular query.

I have a 147 GTA, well looked after etc etc, done 60K ish. Now I've only had the car about 6 months so I'm used what power it has. but I've no idea if it's ever had a new MAF (or the old on cleaned).

So my question is how do you tell if it's ok or if it's on its way out? there is no obvious lack of power (but i don't know what it had to start with) it's not running rich. The only thing that slightly concerns me is that the on board computer shows my avg MPG to be 18. I don't rag it around all day long but i might put my foot down hard a few times a week yet i still only get a shade over 200 miles out of a tank. Also over 3000 - 3500 it seems to pick up more power than at lower revs, but only very slightly.

It's due for an MOT soon so I'll get it checked over at the same time, but if anyone can give me a clue it would be appreciated.

Sorry about this being an essay length post too. 10 points if you bothered to read to the end!

I remember reading somewhere that the maf should be changed at around 65K ish (think it was the evo GTA buying guide) as it is classed as a consumable and no doubt degrades a little over time. I to am approaching this sort of mileage and was wondering the same thing. When I spoke to my Alfa independent about it he was quite clear that you only change it if you are experiencing flat spots or general lack of power high up. But I like you have not had the car that long and have not noticed any of the above. I also understand that attempting to clean it carries some risk of damaging it farther. Though I may attempt this at some point, a new one is not cheep!

had one go in my Seat alhambra diesel some years ago. It basically restricted the turbo boost so the revs would top out about 3k. Not sure what happens in a non turbo injection but I know the tick-over will be lumpy or even non-existent. I bet you'll get flat spots as well. I'm not sure if they have a fixed life but they are exposed to everything the engine sucks in so they can fail. The Seat was at about 35k, but since the repair its done almost 100k more without a problem.

THat's my 2p

A usual sign of a failed MAF is the engine just going flat at a point in the rev range and not pulling any higher unless you only use very light revs.
ie it will drive ok up to about 4-5000rpm, then not go any further.
Almost feels like hitting a soft rev-limiter.