LED questions and general Reef

[BCOrchidGuy]

So, thinking about starting up a new reef, things have changed in the last few years for sure.

Once you purchase an LED system do you need to replace anything like we did with MH and Fluorescent tubes?

Is there an average lifespan I can expect from LED?

What power/ratio should I consider, the old standard was pretty simple, 4 watts per gallon for MH etc.

Any skimmers that stand out as exceptional budget skimmers or anything that should be avoided?

Thanks in advance.

For the record I am considering a 92 gallon corner but am still undecided.