What about we have been friends since along ?
Or
We have been friends since the past to today؟
Or
From the past since now we have been friends?
Or
Our friendship have been continued since now
“since along” makes no sense
“since the past” is awkward and not native usage
“from the past” doesn’t sound right, not standard phrasing.
“since now” is wrong in both examples.
We have been friends (for) a long time.
We have long been friends.
We are long-time friends.
We are old friends. (“Old” here refers to the age of our friendship, not of us.)