This has been mentioned on here a few times before.
From my point of view the advantages are ease of travelling (especially europe/US) and if ever we choose to move to the Philippines my wife can always return to the UK at any point in the future with or without me. I don't think my wife sees the ability to vote as an advantage.
The reasons for doing it as soon as possible is I don't believe it will ever get cheaper or easier in the future.