plain text in start of custom permalink structure

I recently realized it is not recommended to put %category% as the start of a custom permalink structure. So I decided to type my own plain text:

/my-text/%postname%/

and this worked, so I was wondering if what I’ve done will be fine, or will it cause problems? I am avoiding the use of %category% since the codex says it will slow down the site if I have a tone of posts. So, if adding plain text there will solve this (as apposed to using the post ID or another %), then I’m happy.

I’m just looking for some input, or someone knowledgeable to tell me this is a fine way to write custom permalinks. thanks!