The producers are of course able to put all the 1976 colheitas on the market whenever the like. It's just funny that you can have, let's say, two colheitas from 1944, the one being bottled in e.g. 1956 and the other in 2003. From a quality point of view it makes sense that the colheitas are put on the market whenever 'ready', but from a comparison view point it's a bit misleading. For example, two VP's of the same vintage are very easy to compare.
One can argue that two VP's of the same vintage are easy to compare but can be very different from each other, just as two colheitas from the same vintage can be. The main difference, though, is that if one colheita gets to be twice as long in the cask compare to the other, it makes less sense to compare them since they (on paper) are so far apart.
My point is that it would be interesting to see how e.g. the Krohn colheita 1976 would evolve had some of it still been in cask today. Maybe one will say that the one bottled later than 2006 might then be over-the-top since it was put on the market in 2006 because it was 'perfect' by then (or perhaps because the market was ready by then, the stocks were too large, etc) and thus it doesn't make sense to make two different colheitas from one vintage.
Maybe my post is about when and why the producers believe that "now the time is right for the 19xx colheita" :?
Other questions I came to think of when writing the above:
Are there any colheitas from e.g. the 1960's (or whatever decade you like) that have not yet made to the market, i.e. are there any goodies we should all be eagerly waiting for to be bottled and released?
Do "all" tawny/colheitas get better with age (when stored in cask)?
Do the angel's share get too high at some point which makes it too problematic to not bottle the port? (Problematic, as in: too high cost of the bottle compared to the quality, etc.)
The Krohn colheita 1976 has been in cask for 30 years. The Krohn colheita 1997 has been in cask for about 10 years. Is the aging potential for the 1976 far greater than the 1997 because of the time the wine has spent in cask?
Imagine that the Krohn colheita 1976 and 1997 had the exact same grapes that happened to be produced 21 years apart (time machine!), and that the 1976 had spent 30 years in cask and the 1997 had spent 9 years in cask. If I drank both today ---- oh well, I can't remember the question now...

Are colheitas these days younger (in terms of years in cask), than 20-30-40 years ago? Or am I biased because the supplies of younger colheitas are greater due to the fact that they were put on the market just recently?
Are there made any time tables (like this one) that show which years all producers put their different colheitas on the market? It would be fun to see how the producers in some vintages may put their colheitas on the market about the same time, whereas other vintages may yield colheitas bottles 10-20-30 years apart. Maybe a FTLOP project?

Maybe I should stop thinking so much about Colheitas?!
