That is the way to handle it. Many people pick a suggested routine from somewhere and try to plug it into their lives. In reality each of us have different lives and are at different levels of fitness. We have to pick something that fits into our lives and we have to take all the things we do (work, raising children, volunteer activites, etc) into account. Increasing exercise duration and or intensity will come in time. I find people do much better when they start with just a little and work up from there. I've come across too many who attempt to go for it all at once and ultimately burn out.

Good luck!

Joe