Yes there is a mainspar limit.
But if you get one with a reasonable life left in it, it will giveyou years of service. The other thing I forgot to add is that the internal trimmings can get pretty beat up in the PA38. And are very expensive to replace. Its a very basic trainer which does the job it was intended for.
Also as well I prefer the low wing trainers for teaching circuits and it also makes it alot easier refueling and checking the fuel contents on turn around. This really comes into its own when you have pulled the short straw and have 8 hours flying to do that day all 30 min trial flights.
MJ