Whatever type of blades you fit, but two or three sets of them now so you can rotate them as soon as they start to loose their edge.
Contry to popular myth keeping them sharp and in shape actually extends the life of the blade.
At the end of the season go looking for blades as a lot of shops mark then down heavily towards the end of the mowing season to clear some slow stock off the shelves over winter.
At this time of the year they will be dearer as every one draggs out the mower & prepares it for the new season.
