I only have ever lost points if I just had a few left over, that were unbankable. For instance, I currently have 1 point sitting in my account from AKL, March Use Year. It was previously banked and is going to expire, but it is too little to rent out by itself, and all my other points from this current use year are already gone. If I felt like it, I could make a rental by borrowing from next year, and use these points up before the end of February, but that seems like too much of a hassle for just one point.
I have had 5 or 6 points left over, now and then, and have always rented them out, by borrowing whatever else was needed. But I prefer not to do that if I can help it, in addition to the fact that such 'nearly expired' points are generally worth less.
I have rented numerous points that were within a couple of months of expiring, by either doing it myself, or going through the standard brokers. But when you get down that close to the end, sometimes you need to lower prices to rent them out, especially when the only locations left are less popular. I have had to lower my asking price, at times, to $11 or $12. Whereas, I usually shoot for $17 or $18, and I often settle for $14 to $16.
The brokers are often able to place points that are within a month or two of expiring, but, obviously, the more time you have before the end, the more likely you are to succeed.
I currently have some points from the Feb 2020 Use year and the Sept 2020 Use Year that I am just putting up for rent. I expect to rent them out soon (since those points have been banked and must be used) and then I will sit around with the remaining points and if I decide not to use them, I will bank the other points, and repeat the cycle next year.