I'm in a similar position: I'm on a pump with Humalog, I'm insulin-sensitive, and walk my dog for 45-60 mins every evening. Timing is fairly consistent but can vary a bit. Before I went keto, I would down a 200ml glass of orange juice (about 20g carbs) to cover it. Much easier and more flexible than messing around with temp basal rates. Obviously, you'll have to work out how many carbs you need to cover the exercise.
If you do want to use a temp basal, though, I'd suggest two hours in advance is excessive, especially if you're insulin-sensitive. I usually shoot for an hour ahead, but even 30-45 minutes can work well for some people.
(Now I'm keto, my BG doesn't fall as much as it used to, because I'm burning fat rather than carbs. Ironically, I now need the temp basal, to avoid ingesting more carbs than necessary!)