I need advice about the condition of the following procedure:

Synthesis of 2-hexylthiophene (1) n-butyl lithium (2.5M in hexane) (60ml, 0.15mol) was added dropwise to a solution of thiophene (15g, 0.18mol) in 150ml of THF at -78. After 45 minutes upon addition, 27g of 1-bromohexane (0.11mol) were added to the solution. The reaction mixture was then warmed to room temperature, stirred for another 3 hours and poured into water. The mixture was extracted with ether, dried over magnesium sulfate, and the solvent evaporated. The compound was purified by vacuum distillation. 24.2g of pure product (colorless liquid) were obtained. (Yield: 96%)

I performed this reaction many times with very week yield. I changed some condition like leaving the reaction overnight after addition alkylhalide and leave the temperature increase gradually from -78 to 20. Also, changing the lithiation time to be 1 hour. one of my greatest annoyances is the high amount of unreacted alkylhalide!!!! and presence of different di-substituted thiophene!!

do I need to remove the dry ice bath after adding alkylhalide in order to decrease the time of alkylation?

note: I used different alkylhalide not bromohexane