Something to bear in mind which is the harsh truth of some MFC "friendships", is if they were tipping you loads and suddenly stopped when you started giving them free attention, they may well be off tipping someone else when you're not on cam. It's a harsh part of any business that if you start giving it out for free (in this case off cam attention and the ability to be a regular in your room without tipping), they may stop valuing you. You set your own prices, and if that price is free people will think that's what you're worth (or are asking for) and won't tip. These people may be spending elsewhere or are completely willing to spend elsewhere. I've seen this happening a bunch of times in other careers where someone will allow their friend to do work for them for free as a friendly favour then will spend the money they would have spent on more work from someone else.
This might not be happening in your case, but it is something to think about. I actually looked back at some of my chat logs recently and realised when I started there were guys talking to me all the time and always watching me on cam who had barely tipped me anything. I now know that these guys were also tippers of higher camscore models, enough to get them noticed. So essentially they could have tipped me but chose not to.
The bar analogy is pretty good, though camming is a bit different, also if you're still on your camming snapchat then technically you're still in your area of work. Because the nature of webcamming includes company, conversation and entertainment when you speak to members offline it's more of a girlfriend experience relationship than a "hey we're now best friends", unless you literally tell someone they're now your best friend and they no longer need to tip you have you ever really left the bar? You're more just hanging out with them after hours. Kind of like a lock in at your place of work or sticking around for drinks. Bar work is slightly different because your job isn't chatting to customers, your job is serving them. Chatting is entirely up to your discretion. Camming on the other hand for a lot of models is primarily about the chat/personality elements and building a connection with regulars. Personally I don't ever expect tips for chatting offline, but a lot of my regulars do drop a tip anyway if we've had a great chat. It's a really wonderful gesture which I see more like bringing a gift to someones house or taking a friend out for a meal than a payment for time. It's absolutely not necessary but it's saying "I respect and appreciate the time we've spent together", to me it also says "I value our friendship as much as all the sexy things you do on cam". I guess if we go into the bar work equivalent it's like I've worked behind the bar serving people all night and have ended up getting on with them and afterwards they've taken me out for drinks as appreciation.
If you love chatting to people then there are plenty of people on MFC who value that closer friendship, it's not worth it wasting time on people who just want to drain your time and energy and never give anything back when there are so many amazing people to meet! Besides, if they want to be real life friends they should stop watching you on MFC. I don't give any of my real life friends my MFC details so they can come and watch me, I feel you can't have both.
It's difficult to talk to members about their tipping habits without seeming money hungry, confronting these members directly will likely result in fall out so if I were to offer advice I'd say try to do it indirectly as politely as possible. Possibly just being really clear by saying pm chat is now limited to regular tippers as you want to focus more on live camming as offline chat is consuming too much of your free time, but that they're welcome to chat and hang out in your room. Thank the chatters for their time as you explain your circumstances have changed, if they make a fuss then keep your response simple. They have no right to demand your time and they know it. Then they can choose if they want to tip or not without you directly asking them to. Either way, if they're going to leave, you haven't lost anything in tokens or in friendship because no true friend would leave like that. You've basically got nothing to lose.