+3 to +10 = 70% - super easy, 3ews for 2 pluses
+10 to +15 = 50% - still easy, like atr stones about 12ews for these 5+
+15 to +20 = 30% - still normal, 1/3 should be about 18-20 ews for these 5
+20 to +25 = 20% - a little bit harder, will need like 30-40 ews, depands on luck very much here.
+25 to +30 = 10% (for weapons only.) - hard part, will take some time, but not 1 year. like 10-20ews for one plus, again luck is your best friend here.
so it may take 1 year, depends how hard it will be to get ews.