With orarions on?
What do you mean by "senior"?
If he doesn't feel like doing something he gets to tell the other servers to do it for him
LOL, I guess it could be that. I think of it as being entrusted to instruct new ones. Your also usually expected to be the one to clean up the altar area: dusting, sweeping, cleaning candle wax and replacing candles, filling the oil, trimming candle wicks, making sure the table of preparation has wine and water ready (usually in glass containers), cleaning the censer and other brass & metal things, making sure there is enough incense, and coal, organizing liturgical books and supplies, cleaning icons (usually with Rose Water), making sure icons are in the right places (people take them down for veneration and misplace them after), and sometimes making sure to remind the Priest to do stuff, like bless icons or holy water.
Individually those are small jobs, but together it could be an extra 10-30 minutes depending on how bad things are.
The other altar servers help in the service and may help clean, but I think it's good to have at least one person dedicated to the job so it always gets done.