We almost have to keep them on some Pre-emergents year round in Texas because there are so many weeds. I do like to spot treat weeds after I get the lawn under control. Some lawns you just pull a handfull of the weeds. Ultimately the goal is less reliance on weed control and more on good maintenance. I love the adjuntives to build up the turf. It takes about two seasons to see the real results but really bad yards will look improved in 4 to 6 months depending on the expectations.