Delete Wordpress post revisions older than x days

Delete post revisions older than 10 days:

DELETE FROM wp_posts WHERE post_type = 'revision' AND post_modified_gmt < DATE_SUB(NOW(), INTERVAL 10 DAY)

Delete post revisions older than 2 months:

DELETE FROM wp_posts WHERE post_type = 'revision' AND post_modified_gmt < DATE_SUB(NOW(), INTERVAL 2 MONTH)