If this lanterns output varies slightly (i.e. flickering, etc.),is that normal?

Nope, Should be pretty stable, I've found over time that the 'Tiny' jet get a little blocked, you can remove it (undo the two little side screws and remove the lantern head, then you'll see the tiny hexagonal jet), if you take the filter out of the inside of the jet (looks like cotton wool), then heat the jet up with a lighter or similar and then drop it straight into cold water (will fizz a little), that seems to clean the jet out. Note: the jet will slowly get blocked with liquid LPG(butane) pouring through it, which is sometimes neccessary to get the auto (not) ignitor to work, ala tipping the lantern towards the ignitor as suggested elsewhere in this thread. Hope that helps.