D's will put tons of effort into GA runoffs, but typically special elections turn out the most motivated voters and R's outperform. My suggestion for R's would be to get Bloomberg involved in bankrolling the D's - that seems to be a guarantee of success these days!
And for those worried about Collins being able to go rogue, don't forget about Romney and Murkowski. Those 3 will be incredibly powerful for the next 2 years.
I was also hoping that after R's were on the defensive with so many more seats up this cycle that 2 years from now things would switch. Unfortunately I saw that 2022 is something like 22 R's and 13 D's up for reelection, so they'll be on the defense once again.