3 sentences

1. 集邮是他多年来的兴趣。

   jí​yóu shì tā duō nián lái de xìng​qù.

   Stamp collecting has been his hobby for many years.

   Source: Dong Chinese Dictionary

2. 他从小就对集邮非常着迷。

   tā cóng xiǎo jiù duì jí​yóu fēi​cháng zháo​mí.

   He has been fascinated by stamp collecting since he was a child.

   Source: Dong Chinese Dictionary

3. 他最近钻进集邮的学问里，每天都在查资料。

   tā zuì​jìn zuān​jìn jí​yóu de xué​wèn lǐ, měi tiān dōu zài chá zī​liào.

   Recently, he has been immersing himself in the study of philately, looking up information every day.

   Source: Dong Chinese Dictionary