The House ethics probe of Ways and Means Chairman Charlie Rangel (D-N.Y.) will stretch into its sixth month next week, but individuals familiar with the chamber’s investigative process suggest there’s little way to predict when the inquiry will wrap up.

“Six months in an investigation with four or five separate key allegations is not, if you’re looking at something from the point of view of an investigator … an outrageously long amount of time,— said Rob Walker, who served as chief counsel of the House ethics committee and then the Senate Ethics Committee before leaving Capitol Hill to join the law firm Wiley Rein.

“It certainly seems longer in part because that’s one-quarter of an entire Congress,— he added.

According to records maintained by the House ethics committee’s Web site, similar investigations in the past decade have spanned a scant two months to more than two years.

The Committee on Standards of Official Conduct, as the panel is formally known, established an investigative subcommittee in September 2008 to examine multiple allegations against Rangel.