Most people will work, have a family, and other commitments, so when you do go out and ride your bike you need to do it at a high intensity.
The more time you can spend on your bike, the better, but if you’re looking to crack cat. four racing then you need to make sure you ride hard when you do get the chance to ride your bike.
You need to train for the demands of the event, whether it’s a criterium, an undulating road race, or a hilly circuit. Look at the demands of what’s coming up and tailor your training to it. If it’s a crit you don’t need to spend days out in the hills, you need to train your body to riding hard for an hour, with lots of short, sharp accelerations.