Actually, my piece of advice is based on precisely the exact situation that you describe: "After riding one bike for 5-6 hours, and switching to another, my brain maybe goes to the wrong shifting position once or twice, before adjusting perfectly fine."
Up until very recently I owned four bikes with four completely different shifting paradigms:
- SRAM eTap (left paddle moves chain to larger cogs, right paddle moves chain to smaller cogs, both paddles simultaneously flips the status of the chainrings)
- Campy Record (large lever behind the brake lever moves chain to larger cogs/chainrings, thumb lever moves chain to smaller cogs/chainrings)
- Shimano Ultegra (the brake lever itself moves chain to larger cogs/chainrings, small(er) lever behind the brake lever moves chain to smaller cogs/chainrings)
- Suntour downtube shifters (pulling lever towards you moves chain to larger cogs/chainrings, pushing lever away from you moves chain to smaller cogs/chainrings)
So yep, every time I grabbed a different bike there was a moment of "mental recalibration" required, and even then there was usually a biffed shift or two during the ride. Great way to build new neural pathways, lousy way to miss the jump in a breakaway.

But why would you want to biff that shift once or twice when there's not necessarily any other advantage to adopting an alternate shifting paradigm?
The OP rides Ultegra (see shifting paradigm #3 , above). The advantages of eTap (shifting paradigm #1 , above) are well-documented and exist irrespective of how the shift is actuated. Moving from Ultegra to eTap would be considered an upgrade, and therefore worth some "mental recalibration" and/or biffed shifts.
Moving from Ultegra to SRAM Red mechanical (shifting paradigm not yet described; feel free to condense Double-Tap™ to some pithy description) offers no demonstrable advantage [sic], it only offers a modest weight savings. Why would you want to bother putting your brain through that for no payback? It's not worth the upgrade.