I think as long as you keep the nicotine consumption in check, vape to your hearts content, although i'm still relatively new to the game. I enjoy the act and flavors very much, so until a definite reason to quit entirely presents itself, i'm happy just vaping away while trying to continue to lower my nic intake.
I started at 24mg and since i vape quite a bit, I could feel my heart beating a mile a minute by the end of the day. Let's not forget there are negative conscequences to nicotine. Increased heartrate, blood pressure, etc. It's not completely harmless. I bumped it down to 18mg, and now i'm in the process of getting down to 12mg (right now i'm about 50/50 gotta use up the old 18mg juice). If i can get down to 6mg and still get a satisfying TH i'd love to do that.
At the end of the day i'm sure everyone will have a different opinion, but the way i see it, if you enjoy something, and there's nothing to prove it can be harmful long term, why quit? We're so used to being scorned for being smokers and always having the 'end result' being quitting entirely. Whenever I say that and people suggest 'but you're still an adict' I just laugh and remind them of all the things people are "addicted" to. Caffeine, sugar, fast food, crappy reality tv (HA, way more damaging, am i right?) and no one seems to scorn those people the way that smokers are scorned. Just my 2 cents