In terms of Shakib and Tamim almost learning their own game in Test cricket, it is exceptionally difficult for them, Tamim in particular, he has played more than half his first-class matches as Test matches, so he's having to learn on the job, in Test cricket. They don't have the depth to be able to bring him out of the side and send him back to domestic cricket and learn more about his trade. I like the fact Pakistan have done a similar thing with Umar Akmal, and he is scoring big runs in domestic cricket.
Tamim is already their main man with the bat, despite being just 22 years of age. I'm not sure what Bangladesh's schedule is like over the next 12 months, but he needs to get himself into a County side or maybe over to New Zealand, and play some first-class cricket and develop and learn about his game outside of the pressures that comes with Test match cricket, and I don't mean some meaningless T20 competition.
I don't get the impression Shakib will ever manage those daddy hundreds on anywhere near a consistent basis. He plays his shots, can be loose, and is at this moment in time, well suited to batting at around number 6 in Test cricket. His bowling means he already has a healthy workload, at least he is now free from the stresses of captaincy.