Definitely not! I strength train legs once per week usually in the middle of the week. I typically run a 3 day split hitting every body part once per week (sometimes I'll throw in an extra full body workout depending on my training schedule). More than that would clearly affect recovery and I take at least one full rest day (from both lifting and running/cycling) every week.

I am very careful to allow recovery time and avoid overtraining. I lift mainly to maintain my muscle mass through all of my aerobic endeavors (and because I do enjoy it as well). I balance cycling, running, and lifting throughout the week. Right now it is 2-3 days of cycling, 3-4 days of running, and the 3 lifting sessions each week. I have been biking to work 1 or 2 days weekly (20+ mi each way) and getting a long ride in on the weekend. I am maintaining about 20 mpw of running as well with a mix of speed and distance work. Since the duathlon is the current goal, a mix of the different types of training is necessary. I actually find the altering of workout types to help recovery since different muscles are used (ie alternating running and biking days).