If you think it is going bad, it is too late. But like was said, there is not too much you can do to keep it from failing, unless you just bypass it. My original went out at about 110,000 miles and 6 years old. I've put in two Autozone replacements, each of which lasted about 2-3 years. It has been bypassed for about the past 5 years or so.
If you want to have heat, it is just one of those maintenance items you have to do. I did my last one in about 4 hours, I was planning to do it again when I swapped my dash, but didn't get it in time. So I'll just pull it all again this fall and do it then.