With a ~3 day half life you should expect stable serum levels in around 15 days given that that would be 5 half lives for it to accumulate, although the shorter esters tend to peak faster than that. I will follow the same serum timeframe as any other androgen with the same ester. with the shorter ester boldeones you can generally feel/see a change very fast, i always notice my skin becoming more red within a few hours of starting boldenone cyp, havent tried BU yet however as i like the shorter esters.