Is it ok to increase `innodb_stats_sample_pages` up to large number? MySQL sometimes generates bad execution plan irregularly.

2 years ago, I have increased innodb_stats_sample_pages(default:8) up to 64 and recently changed into 128 because Data Volume has been increased for 2 years.

I think 128 is still small. (128 pages * 16KB = Only 2MB. Am I right?)

Is it ok to increase it up to 1024 or higher? What are the points to consider?

How large value of pages are you using?
Changes to the statistics has plagued InnoDB since the beginning.  Fortunately it affects only a small percentage of queries.

Upgrade to a recent 5.6.  There is a significant improvement wherein the stats are no longer recomputed whenever you sneeze.  It is now essentially possible to set them once and forget them.  The number of "random dives" and which algorithm is used is now less important.

As mentioned, MariaDB (and eventually 5.7) has fancier statistics.