Several times a day: Bookmark a thing (usually marked as 'unread').
Every week or so: Look back at my unread bookmarks. Read, or just mark read because I want to keep a bookmark but I don't want to actually read.
A few times a month: Use Pinboard to look something up that I remember seeing, or I don't - but hope I did actually come across already. Full text search helps here.
I wonder if Maciej would consider getting some browser extensions and mobile apps developed? I've probably paid the same for apps over the years as I have for Pinboard itself [1], and they've generally been terrible.
I'm certainly willing to pay more than I already am for Pinboard if it comes with some decent tools. Something like Promnesia [2] and note taking being integrated would make it the tool I use the most all day, so this would be well worth it.
[1] I'm a paying Pinboard user since 2011 and have been paying for full-text indexing since it became available.