I picked 4-5 different length brads for mine for the same reason and
have not been sorry. It'll take a long time to use them so what the
heck. They take up very little room. Most often I'm using 1" to 1½".

Hyde wrote:

Having just purchased a 18ga brad and 15ga finish nailer, I was
wondering what nail sizes folks here find they use most often. I
realize that this is usually determined by the project you are working
on, but I figured some sizes may cover more needs than others. I'd
like to grab a couple of sizes to have on hand rather than run to the
store each time I need them, save for a project that might require a
specific size. I'd probably be using it for trim work and the
occasional "birdhouse" type projects. With the cost of nails I'd hate
to pick a size I'd rarely need, and thought there might be a size or
two that covers a good range of situations. Hearing what sizes others
might have picked up but never used would be nice to hear too. Thanks
for any advice.

Hyde