Why were these repeated in the 1960's?

[John W King]

I have always thought that in the 1960's very few drama programmes were repeated due to complicated agreements with unions. However, as I continue to explore BBC Genome I find what, to me, are oddities in the repeat stakes.
1) The Long Way Home - first shown in 1960, then repeated in 1961 but then, oddly to me, repeated in 1968.
2 Triton - first shown in 1961 and repeated in 1962. But then, really oddly, re-made and shown in 1968 with a repeat of that version in 1969.
Why? Can anyone out there offer an explanation, please?
I know all but 2 episodes of Long Way Home still exist but none of Triton.
Were these excellent serials ever sold abroad? It would be nice to think PM might have found copies in his search.
Thanks for your help.

[Deleted]

Most of the main VT dramas back then tended to have a customary repeat within a year or two before being wiped (although quite a few notably didn't). Some children's drama as well. I've no idea about those specific instances though, I'm afraid.

[Peter Stirling]

ITV complained in the 1960s that the allotted daily TV hours (decided by the government) were too restrictive as they had a backlog of programmes waiting for a transmission slot.
This meant that repeats were few and far between and if the repeat did not happen within the two year window of the contract then it was usually lost for good?