Aluminium is a fantastic medium to build a boat from, what will lead an ally hull to fail.
1) Corrosion inside due mainly to contact of dissimilar metals = insulate with plastic sheet. i.e. if a bolt is used paste with 'DURALAC' liberally.
2) Corrosion inside due to battery
acid or fume, be very careful of the yellow electrolytic paste used to raise conductivity on terminals = deadly and quick corrosion.
3) Concentrated salts from a leaking hose especially if the leak is carrying oxides from dissimilar metals, ie a dodgy hose clamp of inferior grade.
4) You must electrically connect all the ally tubes or pipes used for drains etc by running a wire under the hose end to the other hose end.
5) Dust/dirt/hair/fluff when mixed with moisture will set up a cell of corrosion.
6) Dont inbuild water
or sullage tanks
into hull use fibreglass only.
7)Run seperate earths.
8) Use nylon composite skinfittings and seacocks.
1) Once again insulate with plastic sheet/DURALAC every dissimilar metal connection.
2) If painted repair chips, a metal hull must be maintained as corrosion cells get in under the sharp chipped paint edge and oxide will bubble forth. (STEEL SAME PROBLEMS)
Never fibreglass an ally hull, it's NOT a core
Ally requires oxygen to form an oxide to defend from further corrosion, if painted it must seal 100% this i guess is the best tip to keep aware of.
Get an anode specialist, in Australia
i use 'Wilson and Walton' to calculate anode requirement and measure latent/stray voltages. They used to give you anodes to drop into marinas
attached electrically to the boat to prevent stray currents from underwater cables
and marina wiring
from actively stuffing your hull up.
Good design will alleviate cracking ie panel strengths etc.dodgy welding is probably the greatest let down, i have 40 years experience in ally and get quite shocked at some welders methods ie Cold welds, welds not running around the end of a stringer, frame or bracket and say 1 inch up the opposite side, if not done cracking will start there.
I cannot put a life on a good well built and maintained hull, indefinite really.