It depends on what I've been up to that day or week or month. On average, I need at least a ratio of 1:5 hours out of the day for alone time. This does not include significant others. I do not require much time apart from him
but it's nice to do your own thing while still near one another. I guess I would then have to define "alone time" as being
entirely alone (so, no communication through online mediums or texting) and sans SO being a factor.
If I am being forced to socialize, I require a ratio of about 4:5 hours out of the day alone directly after the event. I get burned out by forced interaction. Something that isn't forced and is minimal contact with others would require recharge time of 2:5 hours just to make sure I'm eating and sleeping properly still. I can easily go too many days in "Party Mode" and not eat/sleep properly as a result. I can perform optimally no matter what mode, but it's going to cost me later.
I've gone through periods of time where I will self-isolate for months from friends and even family. This happens more rarely as I get older, but it was pretty common for most of my life.