I like to mix it up.
I'll weight train for 5 days a week in a cycle that its muscle groups with compounds twice a week. I.e mon-chest tues-arms wedn-legs thurs-back fri-chest sat-cardio sun-cardio then monday-arms tuesday-legs wed-back thurs-chest friday-arms sat-cardio sund-cardio. So each week also a certain muscle group only gets a 4 day rest and this cycles around groups each week. I work in the rep range of 8-12 After a few weeks of doing this my body feels like it going to fall apart, then I switch to doing 3 days a week, for example, monday- back and arms wednesday- chest and tris then friday legs. During the 3 day a week period I chill a little on the cardio too and concertrate on very heavy weights and reps in the range of 5-8.
I will repeat the 3 day fir two weeks, building the cardio right back up then move back to 5 days a week with higher volume.
Ive been doing this for about six months now and it works really well for me.