How long will seeds last?

i found a little ziplock baggie full of seeds and it said L Weed. Now i have no clue how long they have been in the spot i found them but im guessing a couple of years at least r they still good? there all big and pretty dark they look like good seeds

Seeds can last years and years and years. Only way to know if they are still good is try and germinate a couple.

Let us know how they go

A little trick for you. Take a few of the seeds you're interested in and put them in a container with a little water. They'll float at first. Leave them. The viable seeds will sink within 24-36 hrs, or sooner. The remaining floaters have no embryo. You can plant the saturated seeds in a slightly moist, but not sopping wet, medium . . . do not over-water or the pod may rot. You can even use dry soil, as the saturated seeds are well, saturated.

I've rarely found "dead" seeds among properly stored ones. They last forever, it seems! Proper storage = dry.