Ayy, I think it would be a generally smooth transition for you as you do not use 3rd part plugins. I think you can open capx files in C3 even if you are not subscribed, so you could check it out maybe.
One thing you may want to do when you do load your capx in, is convert all your functions to the new C3 functions - it works a bit differently to C2 functions so I'd recommend checking out the C3 manual on functions. This might cause problems depending on how you use functions in your original capx.
I can relate with you - I sometimes don't develop anything for months at a time - but thankfully this year, Scirra have started offering monthly subscriptions, which is great as you could just unsubsribe when you realise your time is limited. I've found I've not used C3 for some months and have saved money by unsubbing (my subscription recently ran out again as I'm working on a project in C2 that doesn't really gain much from being ported to C3, not to mention I use a lot of 3rd party plugins and it's a pain to delete 3rd party plugin events in c2 and need to cross reference from c2 to C3 to recreate events/actions).
C3 is great! It's very comparable to C2 and the fact its in a browser doesn't ruin anything really.
The recent scene graph feature makes it really easy to pair up objects, rather than needing to make a variable for each objects.
Some things will randomly catch you out, like, the "Crop" scaling mode was removed in c3, even though some of my projects depend on this for dynamic screen sizes with UI positioning and such. But this can be worked around with the other options and some events.
One hot take - I don't think there's anything you can do in C3 that you can't do in C2. C3 makes some things easier, but in the end, you could have made whatever you were trying to make in c2, though you'd have to rely on 3rd party plugins for this.
I'd say check C3 out for a month, it's a great bit of kit.