I only discovered these games a week ago and was enjoying the demo on the dev's website. I saw that the game was on sale but then got bogged down by work really hard in the last few days so I missed the sale period. I was wondering if anybody knew how often/when this game would go on sale again as I would like to keep playing it.

Apologies for the weird question haha.

When I want to look at frequency and amounts of sale prices on GOG I go to https://www.gogdb.org/ where they have data that tracks that stuff. Just search for Avernum and it will show you all the games in the series and your can find the sales data you're looking for.

BTW, I am about 2/3 of the way through the most recent version of the first game, Escape From the Pit, and if old school RPG's are something you enjoy, you will definitely have fun with this one.