I've lived most of my life in bikeable regions --- not too hilly, not too car-fanatic locals, not too hot/wet. Especially on the flat regions you happily ride around on far worse bikes than yours, it's just transport that may get vandalized/stolen.
Wanting to travel when young, we naturally did it on bikes: Take your regular camping gear, strap it all on, save loads on train fares and hostel costs (by camping wild, which is harder by train, as it dumps you in urban areas mostly). My first major trip started with a far worse bike than yours (six gears 'mountain bike) and badly packed (rode 5 difficult miles to friend whose van would drop us 1000KM sun/southward, then dumped 10+ KG of stuff, then actually wore binbag for shirt during five rain-drenched days; wore boxershorts in jeansshorts), but pure youthful energy powered us over 2000KM and some mountains in 20days. I lost the others in the downhill bits, as I couldn't peddle above 28KMH (it just destabilized; better flatten myself) while they could speed up by lightly peddling till 35--38KMH; and in the uphill bits I suffered on my 1x6 speeds, versus their 3x7 touring or 2x8 racing bike (circa 1995): 1x6 is like 3x6 with the front one always fixed on the big gear!
It took months to recover (badly-sized bikes causing knee-pain, giant irritations from those shorts), and then the frame of the #$%! bike even tore apart while cycling --- but the next bike was a bit better and clothes more sensible etc, and each year we've been doing similar rides (shorter times but similar distances) alone or together.
So... Know yourself and find out what balance of rides you'll make: I've never had a dedicated holiday bike, so it's almost always been 'hybrid'/'tourer' bikes that I commuted with during the year --- a few were cheapest Decathlon Rockrider mountainbikes, because of daily life (bad roads = knobbly tires for comfort): It's a holiday, so 1% or 5% faster who cares. Similarly, if you're not competing against others, any reliable bike will do: Maintain it, and improve your own times if that's your mindset... [Actually, if you upgrade your bike you're cheating in the competition against your own times/distances!!].
Imagine you live next to a mountain: Riding halfway up it on a cheap unsuitable (1x6 speeds, knobbly mountain-)bike may cost exactly the same effort as all the way to the top on a great bike. So if that's your daily workout, the cheap-halfway option will work out much less than half the cost of the other (wear and tear included), and in case of breakdown you have half the walk home, plus less chance of theft etc. But going slower, you'll have less options/variations in routes: Say you live on an intersection, on a grid of roads, with all blocks 1x1 KM. Then a 2KM ride only allows you four routes (1KM away in four directions, then back), but a 4KM ride gives you more than thirty (1KM away as before then three possible turns then back home that's twelve; plus four possible blocks to go around each in two directions that's eight more; plus any two of the original routes that's sixteen more). Yes extreme example and in real life the options rarely grow that much, but they significantly do: Look on your local map, choose a A-->B route that is shortest and feasible training with a crappy bike, and now see how many paths you can follow from A to B that are no more than 2x that shortest path... If there's few new paths, maybe the fast-and-expensive option not worth it for you.