I skimp on the groundwork on my older horses. The only thing considered groundwork they ever get is when I am tacking up, untacking, or having their feet done. Mine are never lunged. I usually just tack up (unless I'm going bareback), get on, and go. If they are needing some schooling, I may go trot or lope some circles for a half hour or so and work on their neck and mouth. As for a green horse, after about the first 3 rides, I don't usually lunge them either (unless they have shown a willingness to buck). I just tack them up, get on, and put them at a good clip down a kinda rough trail for 4 or 5 miles. Then I come back to the house and spend time doing circles, working on their bending and neck reining and stops. One thing that I absolutely love doing on young horses is about the last half a mile or so home, I will urge them up into a little jog and if they start to get fast or if their head comes up, I will ask for the stop and a couple of steps backward. Even if they are traveling nice, I will do this about every 5 or 6 strides. It really helps them to travel "with their brakes on" and makes for a nice easy ride when they figure it out. Plus, it makes their stop just uber hard and responsive.
I like that concept and exercise. I'll be trying that with the little mare I'm working with currently. She has a very good whoa, but will be interesting to reinforce that on the trail, especially with a little acceleration before the whoa. Seems like it gives you a good handle on their mind and where it is. Thanks for the tip.
And, to answer the OP, I'm strictly a trail rider, so my horses are exposed to as much as possible. While T is tried and true, due to her failing eyesight, Walka is now my primary mount. So, he is being tested, along with myself, and so far he is doing fine. While he is a little lazy in the round pen in saddle, he is very forward on the trail. So the exercise smrobs outlined will be very handy with his training.
Just to give you a smile, the other night I was on T in the field giving her a little exercise and wondering how much she could actually see. All of a sudden a partridge broke and took flight. Well I had been concentrating so hard on T that I jumped in the saddle and then thought "oh, great, spook your horse why don't you!". T never flinched or broke stride. I guess she's handling her situation better than I am. Smart girl my T.