Infrequently-but I have a range of starters-from 1/2A thru small up to standard heavy duty, so I size the starter appropriately to the engine. I would use an electric starter under the following conditions:
(1) a brand new engine that is set up tight and not responding to hand starting
(2) an old worn engine that has very little compression and not responding to hand starting

It is never the first choice for starting! I also have the following inviolable rules:
(1) The engine MUST be fitted with a spinner nut or spinner
(2) The engine is ALWAYS held backwards against compression-ie prop rotated clockwise until the engine comes up backwards against compression-before the starter is applied
(3) Compression ALWAYS is backed off before starter is applied, and slowly advanced whilst starter is turning engine until engine fires

And I'm selective about how much fore and aft shaft play I'll tolerate on a plain bearing engine-(very little, if I'm going to use a starter.........)

New engines I've used a starter on for the first run: MVVS 1.5cc, Yin Yan 1.47 and 2.47, Russian Elfin 149 replicas, PAW 35, Cox 09 fitted with MECOA diesel head

As with most here-I consider it a tool of last resort, but I will use it in difficult cases. I do not own any large 'converted glow' diesels so offer no comment about its suitability or lack thereof for this category of diesel.

Likewise-at the other end of the scale, I would never consider using a starter on anything smaller than a PAW 80

ChrisM
'ffkiwi'