Ian Maxwell, from Wrexam, was sent down by Caernarfon Crown Court after admitting to seven fraud offences between 2002 and 2008.
A former RAF Pilot who served during the Falklands War, he took £35,000 from Vera Davies, in her 80s, promising income from investments, the Daily Mail reported.
Meanwhile, he used his enduring power of attorney to take £172,500 from her sister Dilys Williams, who died in 2010.
He took a further £105,000 from Judith Rich, who was then forced to seek financial help from her local authority when payments to her stopped.
Judge Niclas Parry told the 61-year-old: “These were despicable offences which have led to financial ruination for vulnerable, elderly victims.
“The case involved a serious breach of trust. Your elderly and mentally vulnerable victims trusted you professionally with their life savings. Some of the money was wasted on items of lavish luxury.”
His defence had said Maxwell was driven to his activities after he lost money in Pakistan, claiming he had borrowed the money to shore up his business, with the intention of giving it back.
The prosecution said £250,000 of the total swindled remains outstanding.
