I think it would be very useful to have a mixed logging type based on point change with added interval logging:
If a point change its value, log it, if it as not changed its value for more than x seconds/minutes/hours then log it.
This kind of logging, IMVHO, could help to keep the best from both logging type :
- track any useful "rapid" change of point value
- keep track of a point value at least any x minutes/seconds/hours
- Improve charts views when the point value changes infrequently
- Improve data export/download when point value has not changed over the selected time range
With this type of logging we could set a "coarse" interval logging (to limit storage of unuseful data) but still be sure to track any relevant point change.