I have found that nearly all mechanicals should be able to be regulated within 45 seconds a day and often better.
The chances are your 5 minute error is due to a damaged or dirty hair spring.
Having said that accuracy , which I used to be obsessed with, no longer has any bearing for me when it comes to choosing which watch to wear. I like to wear a watch for a day so I can see how it performs but I then keep a note of that and leave it as it is.
I've messed more up than I've got right by trying to regulate them myself.