Smarter people than me on the internet calculate that at constant 1g you only need 2.5 years to get very close to speed of light. So I guess you accelerate fast enough and reach 'almost speed of light' very early in your travel and total time is almost as if you traveled at speed of light the whole time.

The closer you get to lightspeed, the slower you accelerate (from an outside perspective). It's actually close to lightspeed for most of the time.

I just used the calc, it's closer to 152 years. Which I assume means acceleration at 1g for about a year to reach .999c, and deceleration for the same time.

I just confirmed with dV= a*t, a year of 1g(9.8m/s/s) gets you just over the speed of light. I think it's more complicated than that, If I remember right relativistic speeds require more and more energy to accelerate so you can't ever "reach" light speed.

Most of the journey is spent traveling very close to light speed. It's not a linear ramping up and ramping down of speed, since it takes more energy to accelerate the closer you get to light speed. Rather you quickly accelerate to near light speed and spend most of the trip working on that last small bit of velocity.

Constant acceleration at 9.8m/s^2 in a given direction will bring you close to the speed of light eventually, but yeah, I'm also not super sure how this math checks out