See Ontbrekende rijen in Exact Online Online TransactionsIncremental via Application.
On refresh and no more often than every x hours compare row count in incremental table with row count from $count. When very different, reload full cache.
Interesting, can we count() from exact API ? I can’t find it in their API documentation.
Yes, the use of count() on OData 3 (which is Exact Online’s OData version) is described in Estimate size of an Exact Online company.