You need to play OTB, not online.
Agreed. You cannot recreate or approximate the OTB tournament atmosphere online. Agreed.
But the question is based upon a fallacy. It is like asking, "How long will it take me to drive to New York City?" Who could answer such a question from a stranger?
Nice illustration. Very apropos. I instantly thought 3.5 hours. I suppose it's egocentric thinking.
It depends on
Where you start from How fast you progress What delays/detours you encounterAnd these factors will be different for each individual.
While it is good to set goals, it is not necessary to reach any given level of skill to get much enjoyment and see the beauty in chess. Goals should be set within the next class level, if ratings are to be used.
Saying, "I want to gain 600 rating points this year" is a lofty goal, but not realistic for the overwhelming majority of players. Unless you are already rapidly improving, 100 points a year would only even be possible by playing at least 50 rated OTB games, or almost a weekend tournament every month. Really? Why so many games/tourneys? I mean, if you just need a +7 score (7 games x 16 pts. = 112 pts.) can't you just go to a few weekend tournaments in your own rated section? I mean if you lose/draw about a third of your games wouldn't it just take, I don't know, 4 or 5 tournaments?
Whatever your goals, never forget chess is above all else a game, it is supposed to be fun. Don't put so much pressure on yourself to make arbitrary numbers, you will miss out on much of the enjoyment of the game. 100% agree.
Oops, that's true, the number of tourneys you play in limits your rating's progress.
I was thinking in terms of an 1800 playing strength, not an 1800 rating.