As oppose to Connor Mc Gregor who is prepping for Jose Aldo, you don't have prior knowledge of when the next drooler will jump you or where you will be. Therefore you need to be in an acceptable condition all the time. It is impossible to be in peak condition all year round. And if you pull it off, you will have sacrificed your tactical training (Counter ambush simulation and tool development) for extra time in the gym. Remember... training time is at a premium. You have jobs, family, girl/boyfriends, social obligations and whatnots. It is never a perfect scenario.
The following is aimed at John Q. Public. In a good scenario, you have maybe 10 hours of time you can free up/allocate to activities for yourself . First accept that you will not turn yourself into GSP. Second accept that your tactical ability, tool development, is more important than your benchpress. I know some of you are students and great if you have tons of time, but some of us are lucky to have that 10 hours. Back ob track. So your goal here is two fold; 1. Find the most time efficient way to train and 2. Find opportunities to squeeze in exercises in "non allocated times" for exercises. Examples stairs at work, push ups at breaks etc...
I feel (and please add your own ideas in the comment section) that conditioning circuits are the best. All one needs is his own body weight, maybe a few KBs, med balls and you can do 20 to 30 minutes of intense exercises that will at least give you enough fitness that will be transferable to self protection. You can use these circuits to "pre fatigue" before a scenario, to simulate a situation when you have to engage after a chase and you are already exhausted, whatever.
Be smart, train smart