Can Naruto go into Sage Mode repeatedly by using idle shadow clones? Naruto can apparently have only 5 shadow clones gathering natural energy to enable his sage mode. Why not use the following approach?


Create 4 shadow clones for storing energy and one shadow clone doing nothing (at present)
When one shadow clone is released, have the idle shadow clone create another one.
Repeat as long as required


This way there will always be 4 shadow clones gathering natural energy and there will be no limit of times Naruto can go into sage mode.

Please bear in mind that I've not read the manga and have seen the anime episodes till 264.

Thanks
Every time shadow clones are created, the user's chakra is divided equally among the clones. If a clone creates further shadow clones, that clone's chakra would be evenly distributed among the newly created clones.

According to what Frog Sage Fukusaku explained to Naruto, to enter into sage mode, the user needs to gather natural energy while balancing it with one's chakra. It is difficult to maintain that balance with lower chakra. The user turns into a frog if the natural energy overwhelms the user's chakra. Moreover, if any of the shadow clones turns into a frog, the original user too turns into a frog. 

Hence, repeatedly making shadow clones to go into sage mode increases the risk of turning into a frog, and hence, Naruto cannot use this trick practically.