While "immer" means always, so principally from the beginnig of time to the end of time, it may refer to an implicitly shorter range of time, e.g.,

• Ich trinke immer Kaffee zum Frühstück

cannot literally mean always: I won't have coffee for breakfast after my death, nor did I have it before birth (and not even while I was young), and I might not be able to have coffee under some adverse circumstances.

Adding "schon" adds yet another aspect: First, it restricts the claim to the past, i.e., theoretically to the range from the beginning of time until now (with the same caveats as with the coffee example). But it is nevertheless far from stating that the range ends now. Rather, it suggests that continuuation into the future is expected or even desired.

• Das haben wir schon immer so gemacht (und sollten es deshalb in Zukunft weiterhin so machen)
• Das haben wir bisher immer so gemacht (könnten aber in Zukinft anders handeln)
• Herbert war schon immer ein Raufbold (und wird sich wohl auch weiterhin oft prügeln)
• Herbert war bisher immer ein Raufbold (aber vielleicht kann er sich ja ab jetzt besser benehmen)

While "immer" means always, so principally from the beginning of time to the end of time, it may refer to an implicitly shorter range of time, e.g.,

• Ich trinke immer Kaffee zum Frühstück

cannot literally mean always: I won't have coffee for breakfast after my death, nor did I have it before birth (and not even while I was young), and I might not be able to have coffee under some adverse circumstances.

Adding "schon" adds yet another aspect: First, it restricts the claim to the past, i.e., theoretically to the range from the beginning of time until now (with the same caveats as with the coffee example). But it is nevertheless far from stating that the range ends now. Rather, it suggests that continuation into the future is expected or even desired.

• Das haben wir schon immer so gemacht (und sollten es deshalb in Zukunft weiterhin so machen)
• Das haben wir bisher immer so gemacht (könnten aber in Zukinft anders handeln)
• Herbert war schon immer ein Raufbold (und wird sich wohl auch weiterhin oft prügeln)
• Herbert war bisher immer ein Raufbold (aber vielleicht kann er sich ja ab jetzt besser benehmen)