If remainers are hysterical now, they are going to be apoplectic until the deal is done on the last possible day. Then we have 2/3 years to implement it. Plenty of time. Thats how deals are done.
Not this kind of deal. There are too many things that need to happen between the deal being done and us actually leaving the EU. Businesses are going to start voting with their feet if the basic structure of a deal is not agreed with six months to go.
If you look at the behaviour of the high profile Brexiters, it's clear that they don't think a deal will be done. Jacob Rees-Mogg has been moving his own business interests to the republic of Ireland and saying we are heading for a no deal (which he supports, because he personally stands to gain from it).
Boris Johnson is the clearest indicator. When told that businesses were worried about the lack of progress in the negotiations, he said "fuck business".
He then penned a pretty resignation letter all about how Brexit could have been wonderful but now it won't be and he has no choice but to resign. Having fucked everything up spectacularly for the last two years, he's distancing himself from the government because that way, when we leave with no deal (as he clearly thinks we will) he will be able to say, "it wasn't me!"
He's a glory hunter. If he thought this was going to end well he would want to take the credit for it. The fact that he's running away from it as fast as his legs will carry him is very telling.