My opinion is that the belts themselves are very important to change because of age but the tensioners and water pump is optional depending on what you find. If the original tensioners are still smooth and spinning freely then I'd leave them. Same with the pump, if it's not leaking or making any wrong noises I'd leave that too. It's a personal choice but it's not great shakes to change them later in life if they do fail.
A great mechanic once told me "there's no guarantee a new bearing will last longer than an original still in place". I think he has a good point.
A great mechanic once told me "there's no guarantee a new bearing will last longer than an original still in place". I think he has a good point.