I think you are a fortunate man.😀

So they are offering to be exclusive only with you an d take their SA profile down.  OK.  But do they insist you are also exclusive with them and don't see any others?  If so, that would be a problem.  I guess I'd consider it anyway if they are as awesome as you say.  But I'd be prepared to enjoy them for as long as it lasted without any expectation it would be very long. I guess before agreeing to an exclusive arrangement I'd ask them why they think they want that and find out if it's actually a deal breaker.

I would definitely have a discussion with them both, on frequency of meets, and allowances.  If exclusive, you will be the sole source of allowance, as you know.  I was offered a package deal by a SB, both covered in tats that made me lose interest immediately.  She also stated that they were quite expensive, and so not worth it.  Your deal almost sound TGTBT.  Quite a find though, if it works out and yeah, it may spoil you.  

I’d run with it for as long as possible. Even if it’s exclusive both ways I could be happy banging only them for at least a few months, maybe even years if they really do have model looks. It’s hard to find one really great sugar baby, let alone a pair that are fully bi. Try not to get too spoiled.

...they aren't unicorns and you will grow tired and bored with them as the drama unfolds.  My experience has been poor in that area, especially if all you have in common in amazing sex imho.

"For every hot looking girl, there is some guy who is tired of fucking her" and I think that would go double for two women.

 
Honestly I don't want to be starring in my own porn movie every time I have sex, and I most definitely don't want to have to satisfy two women every time I have sex. Threesomes are great as an every once in a while "treat" but unless you have the libido of a twenty year old, I have found that they lose their luster very quickly.

 
That said, if by "exclusive" they mean once a week or so, I might agree to it, but I doubt I would stick to it long

This could be the ideal of Sugar Nirvana, or it could be just an interesting chapter in your sugar life, or it could end in disaster.  
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Generally, the feedback from this board, and my own observations, is that doubled up SB packages are not worth the effort or are outright scams.  You seem to have possibly found the exception, especially since you've actually converted once with a successful BCD session. But...
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1. How do you "know" (or do you even care) thay they are or will be exclusive? It's a matter of a few minutes to kill a profile and stand up a new one on SA. Also, could you be an addtion to an existing stable of other SD's they already fuck? Maybe they just needed a new "Thursday SD" and found you.
2. How will they "know" (or do you care) that you will be exclisive? Will they expect some proof? Will they try to verify that proof? Whhat will happen if they "catch" you in a lie?
3. What's the sugar spend implication of the twofer deal? Are you getting 2 SB's at a discount (i.e.: Less than twice the "rate" for one SB in your market), or are you paying a premium for the tag team (say, 2.5 to 3 times the "one SB" rate)?  
4. Do you have ala cart privaleges where you can take only one out for a date if the other is not available due to work/family or biology-realted conflcts? And are they open to adding a 3rd (or substitute) SB to the mix?  
5. Are they setting you up for a long term, high-dollar scam? Any hints about buying them a car, funding an expensive overseas vacation, funding a start up business, etc.?
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Just keep your eyes open while they are giving you those amazing double BJ's and be prepared for this candle to burn bright and flame out at any time.  Having no expectations beyond the next date will mean you can't be disappointed.