How far in advance can I make sushi?

Sushi is best fresh. The rice should be room temperature, the cold ingredients cold, the hot ingredients hot, and the nori sheets should not start soaking up moisture from the rice. That's why it is ideally made to order.

That said, I've had some pretty good sushi bento boxes in Japan. This stuff is probably 6-12 hours old. I bought one sushi bento made to order from a 300 year old sushiya in Kyoto and ate it on the bullet train back to Tokyo a few hours later. That was very good sushi for something premade.

I think the quality noticeably declines after 12 hours and it's a shame when the nori in makizushi starts getting sticky because it has absorbed moisture. The sushi bento boxes I enjoyed in Japan had a mixture of both makizushi and nigirizushi.

Clearly there is sushi in US supermarket deli section refrigerator cases that was made a day earlier and some people seem to enjoy these offerings.

It's really up to you to decide what quality you'd like to serve to your guests. And that's not about sushi for this particular situation, that statement is applicable to every meal you prepare.

I suggest you do some test runs, make various sushi and refrigerate then for 6, 12, 18, 24 hours and taste them.

Good luck.