I have them, for the most part, disabled. Ever since the Facebook era I found the overabundance of notifications to actually make me feel worse and more alone. No new notifications meant feeling I was missing out. These days I get notifications for private messages, this seems reasonable. There's also the odd topic I may temporally subscribe to. I manually the topic lists for new replies and eventually back out of checking a topic all together. While I can still get too invested lurking various forums, in general I find having no notifications helps free my mind to seek out face to face interactions.