If stored properly, steroids as finished goods can be good for many years. I have seen where guys run 20 year old gear and there is almost no change in concentration.
most things have a "best by" date for a reason..potency will decrease over a long enough time line. Pharma and UGL gear usually has an exp date. though this is closer to a technicality than reality.
also remember, the carrier oil has a exp date as it is organic. GSO unopened is short like 6-12mo. Personally my first time, i made 40mls..bc each brew you perfect your craft more and more so id start small.