I can't remember where I got this code from and I know I didn't write it. Appropriate credits would be supplied if I knew who to credit. In any case, I thought that you might want to review this code, and use it with the code you wrote.

Code:
 alias fmtdur { 
  ; Usage: $fmtdur(secs [, format])  
  ; Formatting: [y year] [m month] [w week] [d day] [h hour] [n minute] [s second] [u units]  
  ; Using the same character consecutively will zeropad that unit to the given length (ie. n = 7, nnn = 007)  
  ; Doubling the u character will cause it to use the full format (ie. nu = 6mins, nuu = 6minutes)  
  ; Uppercase U characters will capitalize units. 
  var %fmt = $iif($2,$2,wu du hu nu su), %secs = $int($1), %count = $regex(fmtdur, %fmt, /(([^ymwdhns]*)(y+|m+|w+|d+|h+|n+|s+)([^ymwdhnsUu]*)([Uu]*))/g)  
  var %yrs, %mnths, %wks, %days, %hrs, %mins, %i = 1, %fmtchars, %unitchars, %durstr, %amount, %units 
  if (y isincs %fmt) { %yrs = $int($calc(%secs / 31557600)) | %secs = $calc(%secs % 31557600) }  
  if (m isincs %fmt) { %mnths = $int($calc(%secs / 2629800)) | %secs = $calc(%secs % 2629800) }  
  if (w isincs %fmt) { %wks = $int($calc(%secs / 604800)) | %secs = $calc(%secs % 604800) }  
  if (d isincs %fmt) { %days = $int($calc(%secs / 86400)) | %secs = $calc(%secs % 86400) }  
  if (h isincs %fmt) { %hrs = $int($calc(%secs / 3600)) | %secs = $calc(%secs % 3600) }  
  if (n isincs %fmt) { %mins = $int($calc(%secs / 60)) | %secs = $calc(%secs % 60) } 
  while %i <= $calc(%count * 5) { 
    %fmtchars = $regml(fmtdur, $calc(%i + 2))    
    %unitchars = $regml(fmtdur, $calc(%i + 4))    
    %amount = $charpad($replace($left(%fmtchars, 1),y,%yrs,m,%mnths,w,%wks,d,%days,h,%hrs,n,%mins,s,%secs), $len(%fmtchars), 0)    
    if (u isin %unitchars) { 
      if ($len(%unitchars) == 1) %units = $replacex($left(%fmtchars,1),y,yr,m,mth,w,wk,d,dy,h,hr,n,min,s,sec)      
      else %units = $replacex($left(%fmtchars,1),y,year,m,month,w,week,d,day,h,hour,n,minute,s,second)      
      if (%amount != 1) %units = $+(%units, s)      
      if (U isincs %unitchars) %units = $+($upper($left(%units,1)), $right(%units,-1))    
    } 
    else %units = $null    
    %durstr = $+($left(%durstr, -1), $regml(fmtdur, $calc(%i + 1)), %amount, $regml(fmtdur, $calc(%i + 3)), %units, x))    
    inc %i 5  
  } 
  return $left(%durstr, -1) 
}