Any pointers for a strong relationship?
Communication, Talk, talk talk - about everything and anything - Even death and funeral arrangements or cancer etc etc.
Don't let sex be top priority or it will erode everything you've built.
Try always to see from each other's perspective, and it's ok if you don't absolutely like the same things - just don't be condescending about it or harbour nastiness - otherwise, you're harbouring destructive traits and you really should live alone (as you will find this in every person you grow with)
In ways of supporting your partner, sometimes, you might have to sacrifice your patience, or some of your time, or time with your friends, to be with this "best friend and lover" , but nothing too drastic -
As long as each partner aims at putting forth 60% to care for each other, then there's overlap for when times are super tough.
As your relationship transcends years as opposed to weeks, you start to acquire history. It can be overwhelming as you might wonder what you might be missing looking at the green grass over yonder. It's nothing, you're not missing much at all. You also will have to start ALL over again from the beginning, only to survive 3 years more with the new guy before you find out you don't like it every time he smells his fingers after he eats chicken
You should also talk to your partner about monogamy (if that is what you both seek) and revisit this subject every few years. WE men do tend to get a tad boring, so sometimes a relationship needs reassurance that the sex hasn't become something that isn't working anymore or is no longer "enough" - People do change - or ... People finally show their true colours....
I could go on and on. I will stop for now...