Hey Patrick,
I don't use a special template either. I've tried them over the years but the ones other bloggers put out seem to have too much stuff shoehorned in and I spend forever just trying to figure out the functions and eventually give up. I really think the template you build for yourself will be the most useful since it has exactly what you want to know.
Like Jeremy, I use a simple spreadsheet (Google Sheet) with columns for the Card, Issuer, Signup Date, Annual Fee, Minimum Spend Amount, Minimum Spend Due By, and Rewards (to remind me of bonus categories, etc.). In over 10 years of signing up for cards, this is all the info I have ever needed.
Within that workbook I have a couple of other spreadsheets to keep track of my wife's cards, various travel credits offered by cards, and one to keep track of good redemptions (always fun to look back at).
Good luck in your last 5 years! I know what it's like to grind it out with the government
Brandon