I'll give these questions a stab Neil based on my own experience. I think there are lots of misconceptions about these sorts of questions and what it all means in the context of dating/sex/LTRs and the like.
Do her feelings for the first man go away forever?
It depends on many things. Sometimes yes, sometimes no. Sometimes the feelings change/convert to something else.
Do her feelings for the first man go away temporarily?
IF her feelings change (they may or may not) they typically change for good. Why? She has changed. She is no longer the same person as she was in relationship with that particular man. Extremely rare to get that back again because people are not static.
Do her feelings for the first man get put on hold indefinitely?
She's not a tape recorder or a telephone. No. What you look at as "on hold" in my opinion is really that she still loves you and has all along.
Would she really abstain from sex if she loved the first man more?
That depends on her and on the men in her life. My mother-in-law for example only ever slept with one man, her late husband. She had no desire for anyone besides him even after he was gone.
If she is a highly sexual woman, she has needs that she will eventually get met somewhere. She may still care for you. The idea some men have here that it is impossible for a woman to love two men at the same time is unreality. She may indeed love more than one man just as a parent can love more than one child. Each relationship is its own entity with its own dynamic. If she has character and promises exclusivity, monogamy, faithfulness and such that is where her CHARACTER comes into play. She would then chose one man to love to the exclusion of all others. That is why the marriage vows, for example, say "FORSAKING ALL OTHERS." To forsake something is to "renounce or give up something valued or pleasant". So it is a vow to not pursue those other interests or feelings, it is not an evaporation of them. That's why its called commitment in the marriage context.
The high partner counts do not usually develop additional skills because they don't learn the person.
I wanted to comment on this because I think it cannot be over emphasized. My over all partner count is reasonable given the constant bombardment of opportunity, but I am very experienced with thousands of encounters under my belt just in the 17-18 years I was with my ex husband and in the marriage. The sex continually got better (and it was good to start with).
So I would contend that an experienced woman is valuable depending on a man's preferences, more so than a promiscuous woman. Women who are enjoying sex with their only husbands are going to be extremely experienced as the years go by, but you would never consider them promiscuous.
But like many things experience and promiscuity both exist on a continuum but are not necessarily related to one another. Each of us has to weigh how someone interacts with us and also what our own individual expectations are within a sexual context. You only lose your virginity once folks. If you don't marry that person everything becomes relative and each person has to decide what they are comfortable with or uncomfortable with.