Depends how severe and how long for me, but I normally feel OK again in 5mins or so for a mild one, maybe up to 15 mins for something a bit more severe.
I feel better very quickly too.
I had a typical mild one during a walking group walk yesterday. I just took some dextrose and carried on. I was a bit slower for a while both before I realised I needed to treat and for 5-10 min after but can feel it 'lift' and then I'm OK again . (I do use a pump though so my basal insulin was just a trickle, probably didn't lower it early enough before the walk. )
I've had one or two hypos that took longer to get the glucose levels up from but I've never felt unwell after they were back to normal.
The short term symptoms, anything from 5 minutes to max 30 minutes if it's quite harsh, depending on how much sugar you eat to treat it, how quickly it was absorbed, how low you are, how much active insulin you are fighting. The stress response to a hypo can shut down the flow between the stomach and the bloodstream, and that can make it take longer to recover from the acute effects.
Longer term there is a process of restocking glycogen that can cause tiredness and possible further hypos, for me I feel knackered and this often lasts until I have had a good sleep. For this reason a good meal and an early night, and not too much insulin for corrections, is good after a hypo. Impaired hypo awareness can continue 24 hours or so.
I think you're right that it varies from person to person. I started a thread on this a few years back because I found that while I could get sugars back up quickly and the shakes went, I nevertheless regularly felt weak and awful for up to 24 hours afterwards. I find that with me the key is to act as quickly as possible -- the longer the delay, the worse the recovery time. Have you been having problems recovering?
The sheer exhaustion that I experience after a bad hypo lasts for hours and, as Spiker said, I usually need to sleep before I feel any better. A mild hypo is very different though and the effects only last until by bg rises again. A night hypo is a whole different story - I can be out of action for 12-18 hours depending on how bad it was.