My 340 eats distributor caps

My 340 eats distributor caps like you wouldn't believe.
It's a G reg 340gl 1.7 (89) and since ownership at 56k I have fitted two caps and I have now just fitted a third. I think they are lasting on average around 3k each. I clean my sparks and rotor arm regularly but still the problem is there, I am useing caps from halfords, not a good idea I know, but does anyone have any wise ideas on this?

This is a rough list of what I have needed to replace since I got it: radiator, both headlamps, all belts, indicator levers (twice), bonnet catch, boot lock, boot spoiler, most rear end bulbs, drivers seat, rear exhaust box, rocker gasket, window washer motor, seat belt, drivers door lock and handle, both door mirrors, front grill, front bumper vents, steering rack and lower coupling, fuel pipe near the tank as well as the usual service bits, do other 340 owners find they have needed much maintenance or have I been unlucky?

[srtames]

I would say you have been unlucky having to replace many of those items listed apart from exhaust, radiator, belts which are normal but sounds like your oil seal on the distributer needs replacing as it is letting crankcase fumes into the cap .Also check yor breather pipes are clear.
One consolation is that you have no expensive ECU or Cat to replace like newer cars so it is still economical motoring!

regards, Steve