After a few batches that lost their aroma within a week, I moved dry hopping to a sealed keg with a CO2 purge. The difference in shelf life is noticeable — the citrus notes now hold for almost a month.
Soft water is the whole secret. I cut tap water with distilled at 1:3 and add a pinch of calcium chloride. Mash at 64 °C for a dry, crisp finish.
An old fridge, an inkbird controller and a seedling heat mat keep fermentation within half a degree. Total cost was less than a single bag of specialty malt.