Sumerian: *nod* they are thinking they will be busy in real life away from the computer, so they set a vacation day, but during the day they find a short time in which they can pop online for a few seconds and make a move in a few games (or maybe just read a message on a board) and hurry offline again being busy in real life :)

Sumerian: not always the truth .. i have less time to play during weekends than during working days :)

people can set vacations because they know they will be busy that day .. not just because they are actually on vacation ..

Sumerian: could be .. but doesnt have to be .. maybe the person who is online while using a vacation day has only limited time and cant move in all games (i often only move in my backgammon games while i leave my chess games (rarely play them) or froglet games for when i have more time

Sumerian: he could only use 30 vacation days max .. he has only 24 vacation days left so he cant keep using 11 days per move 50 moves long

the total time would be the normal time per move plus weekends without using vacation days .. the vacation days can only add a total of 30 days to the total sum (plus some weekend days which are covered because of the extra vacation days)

4 days per move becomes 6 days per move in most cases because weekend days being added ... would turn into 600 days for a game of 50 moves (minus some because of weekends 'missed') .. this is almost 2 years as well .. so calculating into the extremes a normal game of 4 days per move without vacation days would already take too long i guess

furthermore in your calculation you also assumed you would take 11 days per move as well :)