Hi mate,
My 2002 JTD has a Reddot Racing remap running 153bhp on rolling roads and i've just clicked over to 112,000 miles.
I've no doubt that the remap puts stresses on the engine if you drive it hard, especially the clutch, however things can be upgraded.
My advice;
Make sure EVERYTHING is running as it should be and has been fully serviced,
Make sure cambelt and ideally water pump have been changed (should have been done at 72k anyway),
If you have any further plans for new air filters/induction and/or exhausts then do these first then get a live remap last. This will make the most benefit of the map and tie everything together nicely.
I had no intention of going the whole induction & exhaust route so just had the remap and i'm well pleased with it despite the now occasional engine warning light (see other threads).
My car is used as a daily workhorse covering 25,000+ miles a year, i've had the map for nearly a year and it makes general driving a pleasure with the amount of torque and power to play with.
My Stilo seems to be a very good example as it's been amazingly reliable and i've had hardly any major issues that others have had on here. (goes off to touch wood)
This is partly because it wants for nothing and gets quality parts used when anything is replaced.
If you know the history of your car and you intend to look after it properly and not just mod it and expect it to go for ever then i'd say go for it.
This is just my opinion though and i'm not a mechanic