40 lbs this week.

I found that varying my weight helps keep things fresh.

My "fast weeks" are 30 lbs.

I'll probably bump them both up eventually, but I really like how GoRuck frames it: a mile should take you 15-20 minutes. If you're close to 15, consider adding some; if you're close to 20, consider decreasing weight.

Though more than 1/3 of your body weight probably not recommended.