You should be in the process now... assuming a regular resale, your transaction should take approximately 2 months from offer to closing ( of course your dates will be negotiated and mutually agreed between yourself and the seller ).
Even though it's a bit early .. it's NEVER too early to either:
1) Find the perfect property ... or
2) Familiarize yourself with the market and inventory so when #1 comes around you will know it's value and your preferences and be able to get it accordingly.
All that being said... you'd be surprised, your landlord may be willing to negotiate you an early release or a month by month extension to give you added flexibility. Remember.... everyone focuses on the dollars.. but your dates may make you an attractive buyer as well.
If you have not already... you should begin your process, preferably with someone familiar with the area you are looking to move to.
Best of luck!
Realtor and Broker
Success! Real Estate
Direct Phone: 617.755.8272