The main advantage of keeping accelerating when you’re at >90% of the speed of light is that it means you arrive faster in subjective time. You could take 160 years to get there and use ten times less fuel (or thereabouts), but the subjective travel time would go up by decades.
I think having constant gravity on the ship during the entire flight is also a big plus. Designing a ship where you can live in 0g for years and in 1g for years would be like designing two ships in one.
The main advantage of keeping accelerating when you’re at >90% of the speed of light is that it means you arrive faster in subjective time. You could take 160 years to get there and use ten times less fuel (or thereabouts), but the subjective travel time would go up by decades.
I think having constant gravity on the ship during the entire flight is also a big plus. Designing a ship where you can live in 0g for years and in 1g for years would be like designing two ships in one.