Hello this is a very general question. Disregarding strain type, environment, and nutrients and assuming environment, and nutrients are perfect. If you have a handful of seeds and no clue what they are, and decide to grow them. Is there a typical time frame you would expect them to grow in? Approximately how long in veg then in flower how long? Would it be better to push them to flower based on how long they have been in veg or would you base it on their size? Not over all size because different strains are different sizes, but instead the size of their main stems?
Are all the seeds from the same lineage? Because if they are, the answer is to grow one and find out.
Say the plants will reach sexual maturity in 4 weeks (avg under optimal conditions,) you could be looking at 7 weeks of flowering or 16 weeks of flowering.
No assume you have a handful of seeds and no clue what any are
At this point, I’d shelve them and buy genetics from a reputable breeder because even the most expensive seeds are around $20/per, which is nothing compared to electricity and nutrients. Plus opportunity cost.
But to honor the spirit of your question, because you’ve committed to growing these in this hypothetical situation:
I’d set up to grow a dedicated vegetative tent. I’d budget 8” square per plant initially. Then I’d germinate enough seeds to fill that (assuming 25% cull). Then I’d grow them until they have 8 nodes, and top them down to the 4th, and make a clone out of the pruned top. I’d root/flower all those clones immediately in a separate tent.
What you’d see is a contrast between the eager plants and the late bloomers. You’d observe morphological differences. You could select based on those.
Once you fully flower out the clones, you have an idea of how long they take to flower. Future cuttings from your mother plants should be the same.