If they have been well stored they havent lost any potency in 5 years, oxycodone can mantain potency for decades well stored, 20mg is a good dose for a beginner but not an extremely strong one, if this is instant release you will be fine in 6 hours to take alcohol, if its extended release, you can have a few drinks but be careful, its a myth that you cant mix downers without a tolerance, with 0 tolerance I used to mix oxycodone, diazepam, alprazolam, and alcohol without problems, you just need to know your dose, if you normally use 20mg of oxycodone use only 10 and if you usually take 6 shots or whatever take only 3, mixing downers is extremely dangerous but can be done if you respect dosages, when it gets extremely dangerous is with non standarized opiates like heroin and opium which vary in potency and when you get into very heavy dosages of several downers combined, or trying to take high dosages of all at the same time with low tolerance, if its oxycodone IR its ok, if its oxycontin extended release just take it slow and be careful.