MAGS!
Slick mags have a life limit which is the same a the tbo of the engine.
Slick recommend a 500 hour inspection so under EASA you must do this and I would also strongly suggest it is done anyway.
I can not imagine that FAA reg. aircraft with these mags miss such an important inspection.
You will usually find they need parts at 1000 hours or 1500 hours from new, the odd one needing somthing at 500 hours.
Lets be realastic a 500 mag inspection is around £100.00 + Vat + parts + removal and fitting/ timing.
It should take no longer than a couple of hours for the spannering! The parts however have gone silly at the moment with the $ being strong, mind you so has the price of a new mag.
Bendix mags are lifed at 4 years between overhaul! not inspection!!! Not sure about the hours without getting the book out, stick with the slicks....