Hi CountGarlic, totally understand your concern as i am in the same boat as you are. I have almost 4 yrs of workex and was in the same dilemma till Jan this yr.
Finally decided to take it one step at a time. Gave a diagnostic test, got a decent score so decided to work on it a little to see if there is any improvement. After a month saw a bit of improvement so finally decided to take a plunge and booked the date of 19th May.
Trust me on this, real motivation to study comes only after you have invested a substantial amount on test appointment.
From my experience, it is possible to plan prep along with the job,just requires some serious time management skills. And with just few days left for my GMAT,although I'm quite satisfied with my effort the actual score will tell how well I have managed. Fingers crossed
And I suggest the same to you, test the waters and if they feel alright, just take the plunge. Good Luck. Cheers.