Hi Nancy,
I just wanted to add my 02.
The only "tried and true" formula there seems to be when it comes to the "cardio/strength together vs separately" debate is what works for you personally. If doing strength and cardio together in the same workout works for you/gives you the results you desire/keeps you motivated, then my humble advice would be to stick with it. As long as you are varying the TYPE of cardio & strength activities you are doing (ie, kickbox, cycling, step, aerobics, "light" endurance strength as well as "heavy" muscle building strength) you will avoid over-use injuries and reap benefits from your routine. Some people get better results from keeping their cardio/strength workouts completely separate, others get better results from combining one with the other. If combining, some people prefer to do the strength work first followed by cardio and some prefer vice-versa. Personally, I find that if I do more than a few weeks of combined cardio and strength sessions, I get over-tired, both physically and mentally. I am the type of person who likes to change my routine regularily in order to keep my motivation up. However, you may be the sort of person who prefers a longer rotation, and this is fine too. Whatever keeps you consistent (and injury free!) is what works.
One thing I have learned on this wonderful Forum (and Cathe says this in many of her replies) is that everyone is different. If you are happy with the results your routine is giving you and it is still motivating you, then stick with it. If you feel ready for a change, then change it. Until you actually try something different you just wont know whether it is more effective for you or not.
Isn't it great that Cathe gives us so many choices!? (or in my case, too many choices, he he!).
Anyway, this is just MHO - sorry to go on so long!!
Kaz.