Hallo, Lara. The boots stewards would presumably have done their work like those with the same role in land-based hotels - cleaning and polishing the guest's shoes while they slept. The usual arrangement was for the guests to leave their shoes outside their hotel room doors before they went to bed. In a ship this would have been a problem in rolling seas, so maybe they or the bedroom stewards knocked on the doors and collected the shoes. Can't say I know for sure where the cleaning was actually done - probably in the 'service rooms' which were scattered amongst the 1st and 2nd Class passenger cabins.
Well, a 3rd Class passenger could try putting his boots out in the corridor before going to bed, but it's a sure bet that's the last he would ever see of them!
Yes, they worked mostly at night but there would have been a few available at all times. These men were stewards, members of the Victualling cew. So, from our previous conversations, you must know where they ate and slept.
And I didn't know they were stewards too, so they wouldn't have a definite space and time to eat. I found that they occupied two cabins on E Deck, 6 boots were in the room on the port side of the stairs that lead to their dining saloon (sharing with other crew members), while the other 2 were in the cabin on the port side of the Grand Staircase landing (still sharing with others of course). I'm writing it just in case someone is interested (you never know...)