Do I really want to be a fall back or second choice?
This is a concern of many abandoned spouses when they think of returns. MLCers return, but they do so prematurely and leave again. Not all, but some. They return because they cycle and thus they have changed their minds--they now want you instead of the alienator; this may be genuine, but tomorrow they will change their mind again. They may return because they feel guilty for what they are doing to you or because others--such as parents--tell them that they have to make it work. They may return out of their sense of duty--religious or other. They may return after a break up because the alienator breaks up with them, or the MLCer may break up with the alienator. Maybe they broke up because they want to return to you, or maybe the return following a break up is because they are co-dependent and don't want to be alone.
You need to consider what is acceptable to you. Not all MLCers return because think they are now in-love with you again. Be wary of getting caught up in the idea that the romantic high excitements are indicators of love; they are in-fatuation. Eros-Love is what a couple builds together after the in-fatuation fades; for some the high energy remains, but this is not true for all or even for most couples.
If you allow a return early in MLC, before two years post Bomb Drop, or if he has not left or is just leaving Replay, I recommend emotional caution--more caution the closer to Bomb Drop. I recommend caution with any return, but I want to stress it even more when the time has been less than two years. I know, two years feels like an eternity, but in MLC it's merely the end of the beginning.
If your MLCer has hit rock bottom in Liminality, but has not bounced upwards, again I recommend caution; he has not yet rebuilt his Self. Though as a quivering puddle of depression he may think he either wants to be home or should be--likely because he needs someone to take care of him--he doesn't know what he will want later as he rebuilds his Self. Does it seem positive that he may be seeking you out to help him in such a time of need? Beware. It is both a relief and yet also a danger. Spouses are caregivers, but so are S-Mothers and the line between the two is often indiscernible, before you know it you will cross it and your MLCer will be eating cake.
Even near the end or beyond the crisis your spouse may return because she is settling for you and she feels there are no better offers or because she feels duty bound. Love is work and for the last few years, though you may have been Standing, your MLCer has not been working to salvage your relationship. Her work has been toward destruction and such efforts do not foster love. Your relationship with your returning spouse will be new and thus you must light the fire and build it again. You will become her first choice.