I would leave the "bad sections" on, expose, develop, then trim. It is easier that way and far less risk of getting dust and cutting debris on the surface, which can affect exposure results.
As for age, I use a different brand (Injectorall), which is orange. The photochemistry is virtually identical, though. I have found that older boards require somewhat longer exposure times. I have also found that putting the older boards in a humid box for about 10 minutes before exposing seems to help. I have no controlled experiments, though, on that to support it. By older, I mean 3 years or so. I have no experience with 6-year-old boards. The humid box is just a plastic storage box with a wet paper towel in it.
John