Board Thread:Wikia Discussion/@comment-27279544-20170528163214/@comment-26275332-20170616132851

Also do keep in mind that Baha weapons actually boost you (MC) stats as well no matter what Baha weapon you choose, so building a Baha weapon early on isn't a bad idea and you can make another Baha weapon later since there's no limit of what Baha weapons you can own unlike Cosmos weapons.

Baha daggers are recommended in grids because most top tier characters are human, but you do have the odd grid where you run Baha sword in dark grids if you run Naru (Draph) because she can do really nasty damage enemies on OD on top of being an adorable waifu. So it really depends on what race you're willing to run by the end of the day.

Other than guild wars, you do keep your event materials unless officially stated in the announcement that they will get rid of the mats permanently. Since this idol even contained mats from previous events, I am pretty sure you can keep them forever and spend them afterwards, although I usually buy items ASAP just in case.