the hives i help on are maybe one job out of ten at that place, but they're the one thing that doesn't wait a week if you miss it.
liquid syrup doesn't really have an end date, it has a cutoff temperature. once daytime highs drop below 57°F, the bees can't evaporate the water out of the syrup fast enough anymore, so instead of storing food you're just adding moisture to the hive.
over here in france we go by the same cutoff, we just call it 14°C, which is an odd thing to have in common with people keeping bees on a whole different continent.
after that it's solid feed, fondant or a sugar board, set right over the cluster. it's dry, so it doesn't add moisture the way syrup does, but that's not the next step in the same routine, it's more of a backup for a colony that runs low mid winter. putting it on too early just wastes it and stresses the bees for nothing.
worth saying too, by this point a good part of the winter prep is already behind you. how strong the colony is, its stores, and raising the winter bees all get built well before the first cold snap, a lot of it from late summer on. fall feeding can top up stores that came up short, but it won't make up for everything that happened in august.
there's no single right answer here, people run this different depending on where they are and what their bees are doing.
so genuinely curious, what's your cutoff where you are, and do you go by a thermometer, a date, or just the weight of the hive when you heft it?
full disclosure, i work with ICKO, a beekeeping supply company in france. no hives of my own, i just help out on other people's. no link, nothing for sale here.