i try to get out with my pack every couple days... i have an exo bag that i load with my backpacking gear, then i add weights to the frame. i rotate between 3 different weighted options...
1 - full pack, no added weight - sometimes i won't do this... this is really if i'm feeling tired and just want to take the dog out for a while.
2 - full pack + 45# - minimum 3 miles at a quick pace
3 - full pack + 80-100# - walk for ~ 1 hour. staying safe but making it feel like a workout.
i live in boise ID and have 3-4 trail networks within a mile from my house, so it's pretty ideal for making frequent and quick weighted hikes.
i don't mean to make a suggestion for you as to weight because that should be based on your ability and background. my only suggestion there is like everyone else said - start slow and light. you can always add weight and do it again tomorrow.
more than anything i'd suggest doing some sort of periodization - alternating between long and light, heavy and short, in the middle and in the middle... that way you're as well rounded as you can be.