I read that to be that you want a result with different types of units. Short intervals in weeks and longer intervals in months and very long intervals in years. If so, then use a Case function instead of If:
Let ( I = Get ( currentdate ) - Joined Date ;
Case ( I < 7 ; I & " days" ;
I < 30 ; Round ( I / 7 ; 1 ) & " weeks" ;
I < 365 ; Round ( I / 30 ; 1 ) & " Months" ;
/* else */ Round ( I / 365.25 ; 1 ) & " Years" ;
) // Case
) // Let
Yes sir, this is exactly what I wanted to do and it looked simple enough.
Thank you so much!