Should we have 5 day county games?
If it helps, then yes.
The difference between the ODI and multiple day games is that the different stages of the game are in closer timeframe and you need to be more adaptable.
An ODI have three 'main' stages.
Opening power play
Middle overs
Finishing overs
As long as you have these, then it's fine. You could extend or shorten the game and these will always be there. To have the best understanding of when to accelerate/consolidate as a batting side, or plan your bowling attack in both domestic and international cricket, you should have the same amount of overs. To have difference is to not learn fully.
Other aspects like batting power-plays are still, in my opinion, not being best utilised. The domestic scene would be a potential way to learn to use these most suitably.
The 4 day game have the sections more apart in terms of times. "If" a 5-day game would further the cause and the learning of players then yes, they should introduce it.
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