advice from dad

over the past few years since i've moved out and become adult-like, there have been many times when it's just been me and my dad - talking about life. and i've had the chance to ask him advice on relationships and love. my dad isn't usually one to give advice unless asked, unlike my mom who freely flows with opinions (which i value/have engrained into me), so his words often resonate in my head at times like these. my parents have what seems to be a successful relationship. they hold hands, they do lots of stuff together, they talk -they have sex (gross/inspiring) from what i can see they are quite happy together after 30 + years - so advice from them has some clout.

from what i've gathered, these are a few things my dad believes about relationships:

-marry someone you love, whois your best friend, who has similar values.
-marry the person you would most want to spend the rest of your life with over anyone else.
-keep mutual friends.
-don't go on 'girls/boys night out' style vacations without your significant other (eg. vegas or all inclusive resorts - i think camping and outdoorsy vacations with littl potential for extra marital hookups are okay- i'm a little fuzzy on the details)
-restrict social time with friends of the opposite sex to daytime, preferably public locations - eg. lunch or coffee. dinners, drinks and eveinging home visits are generally innappropriate/potentially sending the wrong message/potentially risky.

then, of course there's the advice from mom:
-your spouse should be your best friend and have similar values
-not advisable to live with someone you don't intend to marry
-communicate
-be a unit/do things together
-it's not wise to marry someone you haven't slept with yet - just in case they are gay.

i think my parents are pretty smart. sometimes the advice torments me slightly as i am still forming my own opinions. but part of me thinks that their opinions have more value as they are in an actual life-long, happy, working relationship - where as i rarely know what the f i'm doing.

as i write this, my bf is at home with a female friend. they had a date to watch a movie that had mutual interest as they both want to work with the director. i just got a call from him around midnight, saying hi - making plans for tomorrow, and telling me that he's thinking about me. it's quite possible that he's discussed me with her. it's quite possible that he's disclosed to her that things are a little shakey (for lack of a better word) between us right now. yet this doesn't bother me at this moment. i'm not jealous/i don't feel threatned. i don't think that there's anything "going on". however, in the long run, i don't know how i feel about this type of socializing with the opposite sex. in the long run, it can't be the wisest choice. however, at this point in my life i'm thinking mostly about the present - which may be why i'm not bothered by this.
i wonder how he would feel if the shoe was on the other foot?
what is the general opinion on friends of the opposite sex when in a relationship?