Tile meets tile

[penandink]

Over on the plumbing forum had several views that where wall tiles meet floor tiles I should use silicone sealant. I can see the logic of this because it allows for movement. BUT just discovered that the wall tiles are tiles upon tiles. Does that make a difference?

Half way round the bathroom at the moment removing the old grout at the junction of wall and floor and the old grout comes out so easily. It must have been there for at least 6 years. (It is a large bathroom). If I replace with sealant that is very difficult to remove when it needs doing in future. Also in places the gap is about 0.5 of an inch - so I presume that those areas I will have to pack with something first whatever I do?

Being old I am not one of those people who upgrades their bathroom every few years in line with the latest trends - so for longevity and ease what do tilers recommend?