That depends, infomike,
Is it common to get involved beyond the stipulated time with a provider? I haven't seen exact stats, but my knowledge of this field leads me to tell you that it is not "common." Does it happen? Yes, of course. But statistically speaking, this board and the self-selected group which posts/reads the messages is small. Very, very small in comparison with the total millions of hobbyists in this world. And I have Staff's word on this, so I'm not making it up. In fact, an overwhelming majority of TER's members/lurkers do NOT read the discussion boards, much less post. They just use the reviews as a means of finding new blood, that's all.
Now, is it common among those who travel The Erotic Highway? Well, yes, judging from the topics posted since the board's inception in May 2006. But among all those who purchase sex for money, it's a minute group that gets entangled in this way, for better or for worse.
As to your doing something right or wrong, my advice is, "if you can't stand the heat, get out of the kitchen." Simple as that. I've said it before, and I'm stating it again: the provider-hobbyist game is an intersubjective endeavor. If you transcend the common boundaries - for whatever reason - and reveal more of your psyche, you will always encounter someone who will reciprocate. In addition, being a provider can get very, very lonely. Needless to say, these ladies are human beings, not robots. If they are in need of friendship and emotional support and you're willing to give it beyond the hour/money/sex, they will gladly accept.
If you are happy the way things are and can maintain your sanity, why bother changing anything? If not, then quit seeing the women in question and simply change. There are some really hot providers out there, successful, classy, truly model material who know how to "play the game." They are not clingy or overstep their boundaries, and still, they make you feel wonderful in bed. But they titrate their responses very carefully and when the time's up, it's simply up. These are women who have other things going on in their generally busy lives and they have other things to do than to hang out with hobbyists post-time. Among the providers I've encountered, these are the career-minded types who go on to become lawyers, businesswomen, etc. and who use providing as a stepping stone. I guarantee that they are far too busy to IM you with their daily goings-on. And still, they will bang your brains out if you let them.
So it's up to you...are you a knight in shining armor ready for any damsel in distress [you may genuinely like this role and then there's nothing wrong with it,] or are you more of a player who practices the 4Fs [find'em, feel'em, fuck'em, forget'em] with gusto? Or someone in-between? As long as you are aware of the role you play and feel comfortable about it, there really is no right or wrong in this BUSINESS...
Yup, let's all say it again,
the Love Goddess