I don't care much about IASW Holiday because my girlfriend and I are not huge fans of IASW, I personally would ride it to see the overlay but it's not something I would care if I missed, honestly. It is a pretty spur of the moment trip, a 2 month advance is spur of the moment for me for a trip like this I guess. We weren't planning on going during the holidays but the way my work and school schedules worked out along with my girlfriend's we would be able to go around the beginning of January. We could go during a less busy time in January if that would be a week or possibly 2 weeks after the dates I listed, but then we wouldn't see the holiday decorations. I know it wouldn't be the end of the world if we missed them but I know my girlfriend has always talked about how she hasn't ever been during Halloween or Christmas and she really likes how it looks with the Christmas decorations from all the pictures and videos she's seen. It wouldn't be the end of the world if we missed them but I think she and I both expect it to be relatively busy at that time as a trade off for her finally getting to see the decorations. And honestly I would really like to see them too, it will be a bit weird being after Christmas and all but still I haven't seen them since I was a small child so it would be very cool to see them again. I wouldn't be back again any time soon, the most frequent I've done DLR trips is once every year or two but I haven't been in almost 3-4 years at this point aside from my free work trip to WDW in 2018. I could wait until the holidays next year but that's a long time away and we'd have to see how schedules would work out that year for any time we could both make it.
Thanks for the input, I will put in some more thought and talk to her about priority of crowd levels vs. seeing holiday decorations or waiting til next year!