I've never been too concerned about luggage weight limits, because most of my trips are for business and I'm only going to be gone for a few days at most. What concerns me more are the carry on luggage size limits. I can pack two or three days' worth of clothing and personal hygiene items in a standard carry on bag, but the airlines keep changing the rules. I hate to check additional bags, because I'm afraid they will get misdirected.
What I ended up doing was creating my own template of a standard carry on luggage rack used by most airlines. I got the dimensions from a travel company's website. It's mostly a wooden mock up, with the posts set at the proper height and width. If I purchase a new piece of luggage or wonder if I've overpacked, I'll put that luggage on the template and get an idea if I'm going to be in trouble at the airport or not.