Mine is a European S40 phaseI 2.0 manual transmission and it has now 220000km (~140000miles). Recently I had to change the battery and alternator because the voltage regulator went out and the battery had boiled! For me this is something normal for such a mileage: everything gets old. Just don't go to Volvo to have the alternator replaced, it is too much expensive. Buy one from an autowreck who has an S40 available.

If you plan to keep your car for some more miles, you will surely have to replace the front lower arms cause suspension balljoints are known to wear out easily on S/V40 (especially phaseI but probably phaseII also). This is also something quite expensive if done by Volvo but buy the parts also from an autowreck and install them yourself, it's really not complicated.

Of course possible things to replace can then be exhaust pipe/catalysor, starter motor, lambda sond etc... and possibly clutch also but mine is still working fine (and this is also a normal wear if you need to change it at this mileage).

Otherwise, if you have something before 2001 model, it is possible that you'll need to replace the font strut mounts and bearings and possibly spring seats also but it depends.

All in all I would say if you're going to make some job yourself it's worth keeping the car because it doesn't cost too much to run an "old" car (no more specific insurances, no more leasing....). But if you do not want to get dirty hand then it's up to you because it may cost a lot if the job is done by a Volvo dealer: f.ex something that I'm sure everybody will need to replace after 100000 miles is the front lower arms. If Volvo do the job, it may cost more than 650$ only for this.....