COBRA Bridge Strategy (45 day pay period)?

I’ll be starting a new position in the next week and have a 90 day period prior to their insurance kicking in. I qualify for COBRA through my previous employer’s benefits, however, given the costs associated with their plan, I’d like to weigh all my options before signing up during the 60 day period.

It is my understanding that I can send in my COBRA paperwork at the end of these 60 days, and I have 45 days to pay 3 months of premiums- am I required to pay that if I don’t have a medical event? My thinking is, if I don’t have any medical events by day 90, I’ll be covered under my new employer’s health coverage- however if I’ll be on the hook to pay for the previous months of coverage, I’ll likely reevaluate my calculus on this (should I use the ACA marketplace? spouse’s benefits plan? short term)?

Not trying to be a cheapass or unethical, but COBRA is a lot of money, and I’d like to have a solid understanding of the system before I chart a course.

I’m in a healthy demographic, with very low prior usage of the healthcare system, however I do participate in somewhat high-risk sports, but would abstain from that until my new benefits kick in.