Zoysia or Bermuda op?
Zoysia - let them spray and treat it, the fungicide treatment for zoysia is very important due to the water retention and high risk of fungus destroying a good portion of new sod.
Bermuda - you should be able to keep it under control yourself if you have time and get soil samples done to see what you may need to focus on, then again the lawn service (if reputable ) can do all the hard work and keep it green.
I like Scott's products for self treating Bermuda, cost will be about 150$ a year for your size lawn and your time spent diy.
I like to alternate bagging and mulching when mowing my parents zoysia I laid 3 yrs ago, It keeps the thatch(amount of dead grass that settles in sprouted grass) at appropriate levels and keeps that zoysia thick and tough.
Bermuda on the other hand should be bagged every time you mow, or else it can grow taller than you may like and retain too much moisture causing water collection and bad drainage.
Try digging up a small chuck about 10 inches deep to see your roots, you want long strong roots with any grass that reach deep and keep nutrients steadily flowing. Do this every few months to stay on point with drainage and overall grass health, weak roots in any species will cause sudden changes when the temp fluctuates.
Or if you don't mind spending the money just let a lawn are professional to treat your investment and keep your property value high.
I have 10 yrs landscaping and lawn maintenance experience.