No not especially, it all depends on how busy your forum is in terms of posting/viewing posts. You will generally notice very poor performance when your access db gets too big.
Having said that, too big also relates to how busy the actual server is, if you are on a dedicated server, an access database of several hundred meg would not cause you any problems, however on a shared server with a couple of hundred other sites you are very limited in the amount of resources you can use, so even fairly small access databases can perform like treacle, just think how your pc would behave if you tried to read 200 access databases at the same time.
I was noticing performance problems for the first time. I am in the process of moving it to a different host which I think will help (CrystalTech) but I don't know because the problem seems to be with Access. I'll probably upgrade it to a SQL Server in a couple of months. It will still be on a shared server. I can't afford the hundreds and thousands of dollars for a dedicated server.
60MB is not too bad for an Access database, assuming adequate hardware. I ran my Access DB to nearly 150MB before converting to MS SQL. It started really taking a noticable hit after 120MB. Your mileage may vary...