Spotlight consuming significant fraction of Disk storage. User response extremely laggy as disk fills. Can I turn spotlight off?

Is anybody else seeing "system files" consuming 25% of hard disk? when I check it is mostly spotlight indexes. I don't want to move more to iCloud as I am frequently in areas with zero cellular coverage. Needless to say as the disk hits 90% usage, the computer becomes laggy when spotlight trying to build even more indexes (4 times now it has become unresponsive when typing this!). deleting the indexes only delays the issue