The expenses system has been reformed now for both houses ( at least, they have for MPs, and I think they have for Peers), which is a good thing. Should be far less cases of abuses of the system going forward.
The length of time these cheats and conmen serve has to be in line with other, similar offences, and whether one thinks the sentences being passed are long enough is likely a subjective decision.There also seem to be somewhat anomalous decisions being made - the case of David Laws being a fine example. If our legal system think it suitable that a housing benefit cheat be jailed, how is it that David Laws never faced a criminal investigation?
This also points to the need for reform of the Lords, if only to stop the frankly absurd situation where convicted fraudsters ( such as Jeffrey Archer, for example) cannot be stripped of their peerage.