TOKYO, Jan 9 (Reuters) - Japanese government bonds firmed on Wednesday, with benchmark yields shrinking away from a 4-1/2-month high hit earlier this week on expectations of more easing from the Bank of Japan. * The 10-year JGB yield slipped half a basis point to 0.815 percent, moving away from Monday's high of 0.840 percent. * The BOJ will consider easing monetary policy again at its Jan. 21-22 meeting as it eyes doubling its inflation target. Any easing will likely take the form of another increase in its 101 trillion yen ($1.2 trillion) asset buying and lending programme, mostly for purchases of government bonds and treasury discount bills, according to sources familiar with BOJ thinking. * Robust demand at the previous session's 10-year sale also underpinned sentiment, market participants said. * "For sure, I think sentiment is turning positive right now," said Le Ngoc Nhan, a strategist at Morgan Stanley MUFG Securities in Tokyo. "But I wouldn't bet on a rally back to 70 basis points, where we were before this sell-off started. I don't think we'll go back to that level again," he said. Benchmark yields dropped as low as 0.685 percent on Dec. 6, their lowest level since June 2003. Nhan said he still forecasts the 10-year yield to gradually rise to 0.95 percent by the end of March. * The benchmark 10-year JGB futures contract ended morning trade up 0.07 point at 143.50 after earlier rising as high as 143.67. * Longer maturities, recently under pressure amid concerns about the new Japanese government's aggressive reflationary stance, also firmed on Wednesday. Yields on 20-year bonds gave up 1 basis point to 1.785 percent, while those on 30-year bonds fell 1.5 basis points to 1.995 percent.