Your existing visa will not be affected if you receive another refusal decision. Each application is decided against the requirements of the immigration rules in force at that time, if for some reason you do not meet the requirements, you will still have a valid visa until 2013. You will then have to make a decision as to what other category of visa, if any, you may be eligible to apply under.
There is nothing stopping you for applying for ILR, however, you must bear in mind that if your application is refused, your fee will not be refunded.
If you wish to discuss, please feel free to ask further questions.
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