Use future perfect continuous tense
they already(rehearse)for an hour when we come .i(work) in this company for 10 years next april.by the next time he (writing) the novel for three years .the thieves are sure that they (drive) for 6 hours when the police discover the robbery on the morning.they (study) for 3 hours when you come

They will have been rehearsing for an hour when we come. I will have been working in this company for 10 years next April. By the next time he will have been writing the novel for three years. The thieves are sure that they will have been drive for 6 hours when the police discover the robbery on the morning. They will have been studying for 3 hours when you come