I usually stop around 2 weeks before harvest at the latest in hopes the neem will be washed off. Through out the summer if I see them I just use neem to do maintenance spraying. If I notice the population is growing I use neem twice a week and if that doesn't do it then I switch it up with insecticidal soap. Spider mites are an issue because they can very easily overwhelm a plant. Since they are so small, people who are not familiar with them wont notice till the infestation has gotten to a point that its very obvious that the plant is being damaged, dropping leaves, very twisted growth and is stunted. Aphids (another monster) do some what the same thing but the difference is that mites are very hardy and build up resistances quickly to pesticides. That is why its recommended to rotate what you using to control them. Eventually they do go away but if not caught fast enough they can kill a whole grow and continue to cause issues down the road.
A friend of mine got mites last fall (which is normal where I live) he tried to control them but they came back with a vengeance so he had to scrap his grow. He thoroughly cleaned out his veg and flower room started back up a month later and boom they were back. So he scrapped another grow. He ended up having to pyrethrin bomb/fog his 2 grow rooms and parts of his house and grow room ventilation to hopefully knock them out completely. So far so good and I hope he has no more issues. His case was pretty bad and he thinks that they were some what resistant and that is why he had such an issue like that.
Once you have them and see the sheer destruction they can cause you will never forget to comb your plants by spot checking and looking under the leaves. The early signs of damage (very tiny white dots) on the leaves will become recognizable. If you start seeing webs then you know the mite colony has gown to a size that needs to be dealt with immediately. Honestly though we grow outside and mites seem to always be around and nature seems to keep them in check for the most part.
Here are some pics for an idea of what to look for (Mainly for people who might crawl to this post) _These are not my images