The fumigation business is indeed risky, as pointed out. Also, and more importantly for Walt's pocketbook, there is a limit to how much they can cook. What will they do in the holidays? Nobody gets their house fumigated in the holidays.
Yes, Walt's already thinking about ditching Mike, for no good reason, just touchy ego. Also, it gives the plot somewhere to go.
The time frame is just silly. Ignore it as best you can. If you can't, you'll have to stop watching I suppose.