Do they try to keep the general times of auction items the same year to year?  I know that it would vary based on the quantity of items they receive, but do they try to keep certain categories at similar times year after year?  Miniatures on Friday later afternoon, for instance.

More or less.  You never know when there might be a major overhaul I suppose (particularly as the webpage itself got a major overhaul this year and now looks beautiful!), but you can generally count on something along these lines:

Auction Opening (9/10 A.M.) running for a few hours, Thursday/Friday/Saturday: Family/Casual (mass market) Board Games

Next: Either more niche boardgames or switching to some other big category (more valuable boardgames, wargames, collectible miniatures, collectible cards, non-collectible miniatures, et cetera)

Mid- to late-afternoon: One or two-hour blocks for others of the aforementioned categories, occasionally featuring a single half hour for the legendary "all train games" section hosted by Tom Wham if he is there

Evening:
Thursday, expensive but not exceedingly rare stuff;
Friday, the "crème de la crème" overall most valuable collectible/rare items in the Auction;
Saturday, T.O.V.A. (Toys/Oddities/Video [Games]/Art, the populist uprising section of the Auction) leading into the final Auction, the Charity Auction (donations ranging hugely in type and value but always lots of great stuff and a good cause)

So the answer really is that people who are interested in the Auction primarily to pick up a random inexpensive game gift for someone or to buy the absolute most valuable things can pretty much know year-over-year when to attend, but for everyone else you have to check the final schedule.