2-3 hours is not a warmup by any logical person's definition.
Do a real warmup of 15min (eg pyramid: increase intensity every 2min until 100% for 2min, recover last 4-5min), or ride around for 30-45min with a couple 1-2 min intervals.
Usually my rides are either intervals or just long rides. If you combine both, usually you do not do one of them properly. If you do intervals right away and zone2 back home, you probably aren't doing enough z2, as z2 should be more than a few hours long. These are basically "junk miles." If you do a regular ride and then intervals at the end, you aren't doing the intervals as hard as you could while fresh, and therefore making them almost pointless.
Choose one or the other: LSD or intervals...but don't do both in the same ride if you want to maximize your gains. But, if you absolutely have to, then do intervals first.