Restocked again.

Questions:

1) I have been on these thyroxine tablets for 20 years now (since my cancerous thyroid was removed in 1994), why do they still only give me two months supply at any one time?

2) Why does the chemist get the 25s from one manufacturer and the 50s and 100s from another?

They're not important questions but they always cross my mind briefly every two months when I pick up my repeat prescription from my local pharmacist.