Nested Paratactic Extension vs Nested Hypotactic Enhancement With Ellipsis

He used coloured chalk whenever it was available and whenever it helped. 

He used coloured chalk	whenever it was available	and whenever it helped
α	x β
	1	+ 2

He used coloured chalk sporadically and whenever it helped.

He used coloured chalk sporadically	and he used coloured chalk	whenever it helped
1	2
	α	x β