Do I upgrade parts for more reliability?

[idie]

My B33 has done me proud for 50 years. If you have a good magneto you know you don't  need electrics to keep going.

[V500]

We can all recount stories of X number of years riding reliable old bikes, and we can also all no doubt recount stories of breakdowns at the worst times too.
Plenty of reasons why a bike stops running, and it's far from just mag problems.