Yes, I like the browser technique. I use Firefox almost exclusively for my MSing. I have a 'bookmark folder' for my bread-and-butter companies that I check daily. I have a new companies bookmark that is companies I have signed up with in the past 3-5 months. I check these about once a week. And then I have alphabetical bookmarks of about 30 companies each that are companies I have signed up with. These I go through every 3-4 months. When I note that a company has gotten a client with decent shops in my area, that company get added to the bread-and-butter folder of bookmarks for a daily check. When a new company still shows nothing after 3-5 months, they get moved out to just the alphabetized lists. It is indeed, as Mert pointed out, musical MSPs. And the companies I worked for most and did the best paying jobs with last year will rarely be the best in the current year as clients, jobs, schedulers and entire companies change.
How much time? With my bread-and-butter bookmark there are currently 34 companies. With Firefox I can have the computer open them all in tabs on a single screen. Firefox has saved all logins and passwords, so it is a simple matter to go from tab to tab to tab and get them all checked within about 30 minutes, though frequently I will check them a few at a time while I am doing other things. I shove the most important ones to the top of the folder so that if I get pressed for time I can at least get those checked daily and some of them I check multiple times per day. While responding to emails about jobs posted sometimes works, I find that as with Jobslinger and other services, by the time the infomation is out there, the jobs are gone.