Extremely simply means very, and neither extremely nor very are used with comparatives, probably because English. I am sure no one would say *LEDs last very longer than standard bulbs.
Note that the modifier very cannot be used with comparatives.
- She is much older than her husband. (NOT *She is very older than her husband.) (English Practice)
You can use very much to intensify comparatives, but not very on its own:
We use very much not very to add emphasis to comparative adverbs and adjectives:
- Omah is very much better than Ian at basketball.
Omah is very better than Ian …
- London is very much bigger than Naples.
London is very bigger than Naples. (Cambridge)
Now, if your next question is, Can we say extremely much longer, then?, I wouldn't go there... :-)
CaGEl records the same restriction in use of very:
Non-comparatives like young allow very, while comparative younger does not: it takes
much, or (with submodification) very much, modifiers which are for the most part
inadmissible with non-comparatives:
- very/ *much young
- much /*very younger (p. 548)
Quirk (A Comprehensive Grammar of the English Language) also records
the restriction on premodification of adjectives and adverbs in the
absolute and comparative degrees with very (see pp. 472-473).
So there you go. With extremely, it should be
In addition, LEDs last extremely long [not
extremely longer than standard bulbs] .