There appears to be two trains of thought as to when to reduce to climb power when taking off in a twin: -

1) Smoothly as soon as the wheels are off the ground (this method reduces the amount of time the engines are blaring at full power and therefore must reduce any stresses - provided of course you are safely clear of obstacles)!?

2) Much later in the climb (this method allegedly is best because it's when the power setting is changed that most engine failures occur)!?

Which of the above views is guff and which is the best strategy?
I'd appreciate any input.

If you're talking about a Perf A aircraft then both are guff and nobody does number 1.

After the landing gear are up, so the airplane will climb if an engine fails.

there is no evidence to suggest this is true. Most Lycoming /Continental engines up to around 400 hp have a max of 5 minutes at full power,so leave levers up agains't the stops for 2/3 minutes then reduce to max continuous.

Keep the power on and the nose up but don't dont let the nose get too high

i fly a PA34-220T (IV) which is indeed rated for 220 hp for 5 minutes.

I don't want to put too much unnecessary stress on the engines, so I always take off with full power and retard to climbing power after gear up at between 300 and 400 feet, obviously above blue line speed (at least 100 IAS), a level which i feel will give me sufficient height in case of a sudden engine failure.

As with all engines, retarding to climb power needs to done in a smooth way

In effect i therefore do not use more than 1 minute of full power

"After the landing gear are up, so the airplane will climb if an engine fails."

At the risk of stating the obvious, this is not necessarily the case with light twins. Especially on the older aircraft where the tired engines aren't producing as much thrust as they once did. Not to mention hot and high thrown in for good measure. And if you're especially unlucky you may experience a downdraught from mountain range or CB-associated vertical/tail gusts.

EU-OPS is now telling us to use maximum power for noise abatement purposes until reaching 800 aal. I wonder if this will reduce engine life and whether it will enhance safety or not?

When you are at a safe altitude that allows you to survive an engine failure.
Obviously depends on make & model and pilot proficiency.
1000 pilots a 1000 opinions.
I felt really comfortable reducing to climb power passing 1000' AGL.
It takes less then a min to get to that altitude and that's where I would transition to a higher speed cruise climb. Anything fails at that altitude you don't have to climb anymore, simply turn downwind.

Keep it simple.

Keep all the levers forward until a safe ht and speed is attained, don't start playing with things too early while you should be concentrating on flight path control ( especially on a dark night )

I was right seat for a low time friend in a PA31 a while ago, after T/O at about 400' we entered cloud while he tried to set CLB power whilst turning onto track. I had to assist him back to less than 30 AOB. He was lucky I was there.

At the end of the day do WHAT THE MANUFACTURER SAYS IN THE POH.

simple.

And if that's too hard then
1/ don't fly at all or
2/ fly a single

in VMC: climb power above 500' agl

in IMC: max power until MSA or 5 mins (if max cont power is lower than full power), whichever is earlier

So on a Britten-Norman Islander or a PN68 Partenavia you leave it on full power until after landing?

Did you mean height and speed? What would that be then? 200 feet agl and blue line (as in an asymmetric go-around)?

Most light twins wont fly too far following an EFATO.

The good Engine only takes you to the site of the crash.

So.............Any height and extra speed in a typical light twin are good things to have, the more the better.

Generally hold the blue line until you are at a safe ht, maybe 500' or so. This assures that you can at least do a circuit at 500' at a safe speed back around to land.

The worst case is short runway, heavy wt and an obstacle. Certain to end in tears if a donk fails just after liftoff. ( sorry if I spelt out the bleedin obvious )