When I purchased my new house, I only realized afterwards that this house had a history of rodents. The previous owners were sloppy and the garage was full of junk, that you only got to see what was truly there until they moved out.
At first I thought the rodent issue was only in the garage, so I closed any possible openings. For several months we didn't have any issues until the winter came. Noticed some interesting burrowed holes in the backyard and in the snow that led to my shed. Laid out a few traps, killed a few rats, then tore down the shed. Found a few rat nests under the shed, but no entrance into the house. It was dumbfounding, as I began to hear the rats in the walls. Tried more traps, killed a couple of more, still heard movement in the walls. Tore down my deck a year earlier than planned, as I need to locate possible entrances into the house. Couldn't find any. After killing all the rats, the mice moved in! Couldn't win and I had to bring in help.
Hired Rich to inspect and lay bait stations. He pointed out that the rats were entering the house by climbing a tree and entering between the brick and siding. I never thought to look up. And the mice were entering through the loose backyard water pipe and/or the dryer vent. Rich laid down traps inside the house, while I sealed off the possible modes of entrances from the outside.
Although Rich offered the 3-month package, he suggested it would not be necessary in my case, as there was no full-blown infestation; but I was not going to risk it. Providing Rich updates, he was able to come by a second time and replace the existing bait stations with fresh ones, which allowed him to provide an update on the possible numbers of mice. With less bait stations showing signs of feeding, the number of mice left over was small. It was definitely a long battle, as the mice began to dwindle in numbers and die out.
I will never forget the loud crunching noises the mice made when eating from the bait stations. It sounded like it was 100x its size. Rich was great, courteous, and informative.